If you're able to login using the Supervisor account, but not any other accounts, make sure the other accounts have the correct permissions setup.
- Login with the Supervisor account
- Go to Administration > Set up system security
- Open the account receiving the error
- If they have "selected group rights", make sure a group is selected for the user's permissions.
- Click Save and Close
If Blackbaud hosts your database:
Contact Support and reference this article.