The backend won't start

Check these in order.

You’re on native Windows

Open Net Worth does not run natively on Windows. POSIX-only file-locking and process-management APIs mean import backend.main fails outright — unsupported, not a rough edge. Run it in a Linux container (Docker) or under WSL2 instead. See Installing Open Net Worth.

A migration failed

The app migrates its database automatically at startup, fail-closed: can’t migrate safely? Takes a verified backup first, refuses to start rather than run half-migrated. The terminal output names what failed.

A backups/db/pre-migrate-*.db file under your data directory is the automatic snapshot — restore it to get back to the last known-good state.
Fresh install, no prior data: usually safest to delete the empty (data-loss-free) database file and let the next start rebuild it.

Not sure which? Don’t guess — the startup log line states it.

The port is already in use

The backend binds to port 8080 by default. Something else there fails startup with an address-in-use error. Stop it, or start elsewhere: make dev PORT=8081 in development, or set PORT for production. See Ports and URLs.

A data file was found corrupt

An unreadable or corrupted stored file is never silently treated as “empty” (which would make the corruption permanent the moment something writes again). It’s quarantined with a .corrupt-<timestamp> suffix, with a clear error naming it. Fix by restoring from your most recent backup, or hand-repairing the quarantined file if you know exactly what happened — the app won’t do either automatically, on purpose.

Still stuck

Check the log file directly — more detail than the terminal shows. See Where your files live for where it is.