Most common cause: time difference between your phone and the Senly server. TOTP codes are only valid for 30 seconds.
1. Enable automatic network time on your phone
2. Wait for a new code in your authenticator app (don't quickly type in an old code)
3. Verify you're using the right account entry — if you reconfigured 2FA, only the newest one works
Still no success? Use a backup code (8 digits) or ask an Admin to reset your 2FA.