I have received an error with Snapshot when I try to run a backup

I have received an error with Snapshot on two different websites. This happens when I try to run a manual backup

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator and inform them of the time the error occurred, and the actions you performed just before this error.
More information about this error may be available in the server error log.