During backup of your Mac, you see the following error in logs:
Request failed. Parallels Desktop is not installed.
As Acronis True Image for Mac has a possibility to back up Parallels Desktop virtual machines, during the disk level backups it sends to the system a request to check whether Parallels Desktop is installed.
In case Parallels Desktop is absent, Acronis True Image writes the result of the request to the logs.
This is just a warning and can be ignored. It does not affect the integrity of your backups in any way.