| Problem | Likely cause | Solution | |---------|--------------|----------| | “Update failed” | Wrong firmware version | Double-check model & regional variant (e.g., B311-221 vs B311As-221) | | Router stuck rebooting | Corrupted flash | Boot to recovery (hold WPS + Power 15s), TFTP restore | | No internet post-update | APN erased | Re-enter carrier APN (e.g., internet, telstra.internet) | | Auto-update greyed out | Carrier lock | Unlock via DC-Unlocker or similar tool |