Error Fixed: 5G Registration Rejected with Error Unspecified 24

Seeing an error message like “5G registration rejected with error unspecified 24” can be frustrating when you’re trying to connect to a 5G network.

This technical message indicates a specific problem during the handshake process between your device (phone, tablet, etc., known as User Equipment or UE) and the 5G mobile network.

These errors are termed as 5g NAS (Non-access stratum) and can be fixed using this guide, which aims to help you understand this error and provide steps to potentially fix it.

Decoding 5G Registration Rejected with Error Unspecified 24 (Cause #24)

The error “5G registration rejected with error unspecified 24” corresponds directly to 5GMM Cause #24 – Security mode rejected, unspecified.

Here’s what it means in simpler terms:

1. Your device successfully attempted to authenticate with the 5G network.
2. The network then sent a command (SECURITY MODE COMMAND) telling your device how to set up the secure, encrypted connection (activating integrity protection and ciphering).
3. For some reason, your device (UE) rejected this command.
4. Crucially, the reason for the rejection wasn’t one of the specifically defined problems (like a capabilities mismatch – Cause #23). So, your device told the network “No,” but without specifying exactly why, hence “unspecified.”

This error usually points towards an issue primarily on the device side (phone/SIM) or a specific incompatibility/state mismatch between your device and the network during the security setup phase.

Potential Reasons for Cause #24

While “unspecified,” common underlying technical reasons could include:

• Issues with the security context or keys stored on the device/SIM.
• A problem with the SIM card’s state or provisioning.
• Software glitches or bugs in the device’s operating system or modem firmware.
• An integrity check failure of the received Security Mode Command message.
• A mismatch in expected parameters (like NonceUE) not covered by other error codes.
• Temporary state desynchronization between the device and the network.

How to Fix 5G Registration Rejected with Error Unspecified 24

Since the reason is “unspecified,” troubleshooting involves trying common fixes to reset the device and network state. Try these steps in order:

1. Restart Your Device: This is the simplest and often most effective first step. Turn your device completely off, wait about 30 seconds, and turn it back on. This clears temporary glitches.
2. Toggle Airplane Mode: Turn Airplane Mode on for about 30 seconds, then turn it off. This forces your device to disconnect from and reconnect to cellular networks, potentially resolving temporary registration issues.
3. Check 5G Coverage & Network Status: Ensure you are in an area with 5G coverage from your carrier. Sometimes, weak signals or fringe coverage can cause registration problems. Check your carrier’s website or social media for any reported network outages in your area (relevant as of Sunday, April 13, 2025).
4. Re-insert Your SIM Card: Power off your device, carefully remove the SIM card, check it for any visible damage, gently wipe the contacts if needed, and re-insert it securely. Power the device back on. This can resolve issues related to poor SIM contact or initialization.
5. Reset Network Settings: This action clears all saved Wi-Fi passwords, Bluetooth pairings, VPN configurations, and cellular network settings, resetting them to factory defaults. It often resolves persistent connectivity issues.
   • On iPhone: Go to Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings.
   • On Android (may vary slightly by manufacturer): Go to Settings > System (or General Management) > Reset (or Reset options) > Reset network settings (or Reset Wi-Fi, mobile & Bluetooth). 
   • Note: You will need to reconnect to Wi-Fi networks afterward.
6. Check for Software Updates: Ensure your device’s operating system is up to date. OS updates frequently include updates for the modem firmware, which handles cellular connections and might contain fixes for bugs causing Cause #24. Also, check for Carrier Settings Updates (often prompted automatically or found in Settings > General > About on iPhone).
7. Check SIM Card: If possible, try your SIM card in another known-working, 5G-compatible phone. If the error persists, the SIM card itself might be faulty or improperly provisioned. Conversely, try a different, known-working SIM card (from the same carrier, if possible) in your device. If another SIM works, your original SIM is likely the issue.
8. Verify 5G Plan/Subscription: Double-check with your carrier that your mobile plan explicitly includes 5G access and that there are no restrictions or blocks on your account preventing 5G registration.
9. Contact Your Mobile Carrier Support: If none of the above steps resolve the “5G registration rejected with error unspecified 24” issue, you need to contact your carrier’s technical support. Explain the error message (mentioning Cause #24 can be helpful). They can:
   • Check your account provisioning for 5G services.
   • Investigate potential network-side issues or incompatibilities related to your device/SIM.
   • Re-provision your SIM card or recommend a replacement.
   • Check for known issues specific to their network or certain device models related to this error.

Understanding 5G Connection Failures: A Complex Process

Connecting to a 5G network involves several complex steps managed by protocols like the Non-Access Stratum (NAS). Failures can occur at various stages, including authentication, resource allocation, and security setup. Your device and the network exchange specific messages and codes to identify problems. While we are focusing on Cause #24, it’s helpful to know there are many potential reasons for connection issues, as illustrated by these examples you provided (based on 3GPP TS 24.501 standard):

• Cause #20 – MAC failure: Problem with the message authentication code during authentication.
• Cause #21 – Synch failure: Issue with sequence numbers during authentication.
• Cause #22 – Congestion: The network is too busy to handle the request.
• Cause #23 – UE security capabilities mismatch: Your device and the network don’t agree on security features.
• Cause #26 – Non-5G authentication unacceptable: An issue with the authentication method used.
• Cause #28 – Restricted service area: You’re trying to connect in an area your plan doesn’t allow.
• Cause #43 – LADN not available: Trying to access a Local Area Data Network outside its service area.
• Cause #65 – Maximum number of PDU sessions reached: Your device already has the maximum allowed data connections active.
• Cause #67 / #69 – Insufficient resources for specific slice (and DNN): The network doesn’t have enough resources for the specific network slice (virtual network portion) you need.
• Cause #71 – ngKSI already in use: A security key identifier issue.
• Cause #73 – Serving network not authorized: Your home network didn’t authorize the network you’re trying to connect to.
• Cause #90 – Payload was not forwarded: Network issue preventing data forwarding.
• Cause #91 – DNN not supported or not subscribed in the slice: Data Network Name (like your APN) isn’t allowed for the network slice.
• Cause #92 – Insufficient user-plane resources for the PDU session: Not enough network resources for your data connection.

This list shows the variety of potential roadblocks. Now, let’s focus on the specific error you encountered.

What is 5G NAS (Non-Access Stratum):

The 5G Non-Access Stratum (NAS) is a fundamental protocol layer within the 5G System (5GS) architecture, acting as the crucial communication bridge for control plane signaling directly between the User Equipment (UE) – your 5G device – and the Access and Mobility Management Function (AMF) within the 5G Core (5GC) network.

Operating independently from the radio-specific Access Stratum (AS) layer, the 5G NAS manages essential functions regardless of the access technology being used (like 5G New Radio or even Wi-Fi in some scenarios). Its primary responsibilities fall into two main categories: 5G Mobility Management (5GMM), which handles procedures like network registration, UE location tracking, connection management (CM-IDLE and CM-CONNECTED states), and overall device mobility within the network; and 5G Session Management (5GSM), responsible for establishing, maintaining, modifying, and releasing the PDU sessions that enable user data transfer.

A critical function managed by the 5G NAS layer, as highlighted in your text, is security establishment and failure management within a specific Public Land Mobile Network (PLMN). The NAS protocol orchestrates the mandatory mutual authentication process, a vital security procedure ensuring both the UE and the 5G network verify each other’s legitimacy before secure communication is established.

If any problems arise during authentication or subsequent procedures, the 5G NAS protocol defines how the UE or the network (specifically the AMF) signals these issues. This includes sending Authentication Reject messages or indicating various Network Failures. These messages typically contain standardized failure cause codes or reason codes (like the list you provided, covering issues from security mismatches and congestion to subscription problems and resource unavailability) to provide specific details about why a procedure failed, aiding in troubleshooting and maintaining network integrity.

Also Read: 

• 5G vs 5G Ultra Wideband
• 5G vs 5G+ vs 5GE

Conclusion

The error 5G registration rejected with error unspecified 24 indicates your device declined the network’s security setup command without a specific standard reason. While frustrating due to its “unspecified” nature, it often stems from solvable issues on your device or SIM card. Following the troubleshooting steps above, starting with simple restarts and resets, can often resolve the problem.

If the issue persists, contacting your carrier is the essential next step, as they have the tools to investigate network-side configurations and potential deeper incompatibilities.