Recreate the scheduled task to solve the issue
This article applies to:
Every hard disk has a unique ID. Acronis True Image searches for this ID to proceed with a scheduled task. Once the hard disk is switched, there is no ID to which the task is scheduled. Hence, the task fails.
Recreate the scheduled task.
If you are planning to switch the hard disk drives, create a separate task for each of them.
This is also true for USB flash drives.