error: [file path] could not be uncompressed or is an invalid compressed backup file. Make sure that you have selected a valid compressed backup and that you have sufficient disk space to extract the backup onto the server's C:\ drive.
1. Extract the compressed database files using a third-party compression utility such as 7-zip or Win-Zip. 2. Attach the database in the Blackbaud Management Console using the extracted BAK file or database files.