Common Causes
- Insufficient disk space for temporary archive creation
- Permission denied writing to temp directory
- PHP memory limit too low
- Execution time limit too low
How to Diagnose
- Check WHMCS Activity Log for the exact error
- Confirm free disk space on the server
- Confirm module temp/storage folders are writable
Fixes
- Increase memory_limit and max_execution_time as needed
- Adjust permissions/ownership of the temp/output folder
- Reduce backup size (exclude large folders if supported)