Troubleshooting

Symptom	Check
Wrong Chain ID	You are not on the production binary, or you pointed a wallet at staging (733100101) or retired v1 (7331).
No peers	Firewall 9333, --connect seeds, advertise address.
RPC GET 403	Use POST JSON-RPC.
Will not start	Configuration checksum, missing genesis decision fields, permissions on /var/lib/nvc.
Height stuck	Disk space, peer connectivity, compare tip with explorer.

Never delete /var/lib/nvc to “fix” sync unless you intend to resync from genesis on purpose.