Umfriend is correct. Acronis relies on VSS, and ... historically has used their own VSS filters (which have caused issues).
Because the pool doesn't support VSS, Acronis may not be able to target it.
If it has a "file backup" option, rather than a whole disk option, then that may work, as it shouldn't rely on VSS.
Otherwise, you'd want to back up the disks in the pool, and not the pool directly.
http://stablebit.com...Backup the Pool
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