If you see a message similar to this:
The password database could not be located. We have restored the database to default settings. If you have moved or renamed your database, you can restore your information by selecting File-Restore and navigating to the database file.
This is most likely caused by another app (most often OneDrive) moving the Passwords Plus CS folder out of the documents folder and into the cloud. When the app then goes to sync, it can’t find the data. To fix this you need to uninstall and reinstall the app so that everything is put back where it belongs.
In order to do this, you will need to know your email address and Sync ID so you can log back into your sync account to get your data back.