Backup of a SharePoint site fails with:
An internal error.
This error might appear when the archive name is longer than 64 characters. Acronis storage has a limitation of 64 characters for the archive name.
In Acronis Cyber Protect Cloud 21.02, the error message has been changed to The backup file name <...name...> is too long. It exceeds the maximum supported length by <...> characters
In protection plan options, navigate to Backup file name and manually change the name to comply with this requirement.
Alternatively, in Backup options set the backup file name to the template [Resource Name][Resource Type]A
This error might also appear under different conditions, contact Acronis support for assistance.