After Windows Update last night, Windows Server 2019 wouldn't mount a storage space volume as ReFS (it appears as RAW). The error in the ReFS event log is "ReFS failed to mount the volume. Version 1.2 doesn't match expected value 3.4" No issues that I can see at the storage space level (it is a mirrored disk). The volume was working fine before Windows Update and the reboot. Another ReFS volume still works fine after the update.