Two phones, and only one works? Only the most recent setup is valid — the other phone holds an older key. Sign in with an emailed code, then open Settings → Sign-in security → Add to another phone and scan it on the second phone.

The app shows no accounts, or was reset? Choose Email me a code instead (or a recovery code). After signing in, use Set up again — or in the app, Restore from my World Space ID if you turned backup on.

Codes always refused? Set the phone's date & time to automatic. World Space Authenticator corrects its own clock.