After a successful universal firmware flash:
| Problem | Likely Cause | Fix |
|---------|--------------|-----|
| Router doesn’t boot after flash | Wrong hardware revision (NOR vs NAND) | Use serial TTL to flash correct firmware |
| WebUI shows “Login failed” | Old browser cache or default password changed | Hard reset; use admin / Admin@123 |
| No LTE signal after flash | APN missing or band mismatch | Manually set APN and scan bands |
| Stuck on “Upgrading…” for 30+ min | Corrupt firmware file | Power cycle (risky) and retry with verified MD5 |
| SIM not detected | IMEI zeroed or SIM lock active | Restore IMEI; then use DC-Unlocker to remove SIM lock |