Registration and Access Failures
Use this page to isolate why a UE cannot complete 5G access or registration. Start with radio access and RRC setup, then follow NAS registration, AMF selection, TAI handling, security setup, and final registration completion.
Start Here
Use these entry points when you need to decide quickly whether the failure is radio access, registration reject, AMF routing, or tracking area related.
Start with Registration Failure
Open the main guide if the UE reaches NR but fails to complete 5G registration or gets rejected.
Check Reject Causes
Use cause-based isolation when the network explicitly rejects registration or related access procedures.
Check RRC Access Path
Use this if the failure appears before stable NAS progression or during early radio access.
Check Core Selection
Use this when the UE reaches registration signaling but serving core selection or routing looks wrong.
Failure Domains
Separate the issue by where the access path breaks so you can avoid mixing radio, NAS, mobility area, and serving-core problems together.
Initial access and RRC setup
Covers cell access, RRC setup, setup complete gaps, and failures before stable NAS progression.
Registration reject and incomplete NAS flow
Covers registration reject, missing responses, stalled NAS progression, and incomplete registration completion.
AMF selection and GUAMI routing
Covers wrong AMF selection, GUAMI mismatch, routing issues, and unexpected serving core behavior.
TAI and tracking area mismatch
Covers forbidden areas, unexpected tracking area handling, and mobility-context-related registration failures.
Security and identity during access
Covers authentication, security mode setup, temporary identity reuse, and identity-related registration failure.
Emergency and restricted access cases
Covers emergency registration, restricted service, and edge cases where normal registration logic does not fully apply.
Featured Guides
These are the main high-value guides for registration reject, early access failure, AMF routing, TAI mismatch, and emergency-access edge cases.
5G Registration Failure Troubleshooting
End-to-end guide for registration reject, incomplete registration, AMF selection issues, and first-access failures.
Registration Reject Cause Analysis
Decode registration reject causes and connect them to likely access, subscription, mobility, or security faults.
AMF Selection and GUAMI Issues
Troubleshoot AMF routing, GUAMI mismatch, AMF reselection, and registration failure caused by serving core selection.
TAI and Tracking Area Mismatch
Diagnose tracking-area-related registration failures, forbidden areas, and mobility context mismatch.
RRC Setup Failure During Access
Analyze why initial access stops at RRC setup, setup complete, or early access signaling.
Emergency Registration Issues
Troubleshoot emergency registration behavior, restricted service, and emergency access edge cases.
Analysis Workflow
Follow this sequence to identify the last successful step, separate radio from core behavior, and narrow the root cause using messages, causes, and timers.
1. Confirm where access stops
- Does the UE camp on NR and attempt connection?
- Does RRC setup complete successfully?
- Does NAS Registration Request reach the network path?
2. Separate radio from core-side failure
- If failure happens before stable NAS, start with RRC and radio access.
- If NAS progresses but registration is rejected, inspect cause values, AMF routing, security, and subscription handling.
- If signaling is accepted but completion never happens, check missing responses and timeout behavior.
3. Check identities, areas, and serving core selection
- Validate GUAMI and AMF selection logic.
- Validate TAI and tracking area handling.
- Check temporary and permanent identity continuity.
4. Correlate logs and message path
- Align UE-side, RAN-side, and core-side timestamps.
- Map the last good message and the first missing or rejected step.
- Use cause values and timers to narrow the failure domain.
Deep Guides
Use these when you already know the rough failure branch and want a more focused troubleshooting guide.
5G Registration Failure Troubleshooting
Main landing guide for failed or incomplete registration from first access to final completion.
Registration Reject Cause Analysis
Cause-first reference for interpreting reject behavior during 5G registration.
AMF Selection and GUAMI Issues
Guide for serving core selection, routing logic, GUAMI mismatch, and unexpected AMF behavior.
TAI and Tracking Area Mismatch
Guide for forbidden-area behavior, tracking-area mismatch, and mobility context problems.
RRC Setup Failure During Access
Guide for failures that occur before or around RRC setup and setup complete.
Emergency Registration Issues
Guide for emergency access cases and restricted-service registration behavior.
FAQ
Quick answers for the most common access and registration troubleshooting decisions.
What is the fastest way to separate access failure from registration reject?
Start by finding the last confirmed successful step. If failure happens before stable NAS progression, focus on radio access and RRC. If NAS proceeds and the network rejects or stalls the procedure, focus on registration cause values, AMF routing, security, and subscription handling.
When should I check AMF selection first?
Check AMF selection early when the UE reaches registration signaling but the serving core appears inconsistent, reselected unexpectedly, or unable to complete the procedure cleanly.
Why keep TAI mismatch separate from general registration failure?
Because tracking area handling often produces a different troubleshooting path from generic reject analysis. It is usually tied to area policy, forbidden areas, mobility context, or inconsistent area configuration.