This means that the backup task creation has failed due to an external factor. In the log, look for the lines preceding the error message to find out the cause
Acronis Snap Deploy started supporting disks with GUID partition tables (GPT) and dynamic disks in version 4.
Acronis Snap Deploy 5 supports GUID Partition Table (GPT) partitioning scheme. Dynamic volumes (in Windows) can be deployed as basic volumes only.
Acronis Snap Deploy 4 supports GUID Partition Table (GPT) partitioning scheme. Dynamic disks currently are not supported for imaging and deployment. Detailed information here.
Deploying the Agent for ESX(i) if it hasn't been deployed automatically during vCenter Server integration
How to receive an upgrade license for an Acronis Enterprise Product provided that you have a respective support option
This is an irregular known issue.
As a workaround, please shut down the Agent machine manually (or through Remote Desktop).