Version 0.12.9 has just been uploaded to Google Play!
This release should fix the issue where a previously failed (e.g. encrypted) database would still be reused, even if a different database (e.g. unencrypted) was selected afterwards.
This behaviour resulted in some cases in the error message that the database is encrypted, even if it was in fact not encrypted (any more).
The workaround for this issue, in case you can’t update to the latest version, consist of closing/killing the app and optionally deleting the application data (long-press the icon, typ on “App-Details” and delete the app data with the option under “Storage”).