The following error message appears when you back up a device with iMazing:
"Cannot back up your device.
Details: The backup does not exist."
iTunes is also unable to back up your device.
This error message results from the default program files path pointing to a drive other than the system drive. iTunes and Apple Mobile Backup do not handle this well, resulting in the inability to back up iOS devices.
The following Microsoft article explains how to reset the default path:
iTunes and iMazing should now both be able to back up iOS devices.