This is a stupid windows issue unfortunately, the app volume path is invalid and it can happen sometimes especially if you move disks around. What you need to check is to see if the appvolume is offline. You can do this using powershell Get-AppVolume. You can then remove the offline volumes or dismount them. For me I had duplicate volumes mapped to different drives which causes issues:
The main issue is the real volume thats online (F drive) is being confused by old volumes on the same drive letter. In the end of I had to clean the volume ID’s out of my registry so I ended up with the correct mapping as follows:
Once done all is ok and FS works fine again.
Hope this helps,
Zooze74