The "Restore from Backup" feature was designed to restore a previous backup without needing to detach the existing database.  The "Restore from Backup" functionality should not be used to restore a newer backup made on a different server.

To resolve this issue, complete the following steps:​
  1. Detach the existing database you want to replace with an older backup. 
  2. Move the database files to a different location OR restore the backup to a different folder as the Blackbaud Management Console does not allow overwriting database files.
  3. Restore your backup using the Blackbaud Management Console.  NOTE: Please remember to click the link "To adjust file destination(s), click here" and select a valid location for the database files.
If you receive this error while restoring a backup while moving to a new server, please refer to how to attach or restore a database to the Blackbaud Management Console (includes video).