This can have multiple causes:
- The UFS file may be incorrectly named. Please ensure the name is identical to the original file and ends with “.ufs”.
- The UFS file may be corrupted. The following article explains how to verify your files integrity: How to check the integrity of my soundbank
- [Mac only] The UFS file might have a permissions issue; locate the UFS file and Get Info (Cmd+I), then change privileges to Read & Write.