Recently I moved some of my VHDs to a different drive, I thought simply keeping the same drive letter should do the trick (as it has in the past) however I was wrong. When I had finished the copy and changed the drive letter I was presenting with an error upon starting the VMs:

I assumed it was permissions so did a quick search, however the easiest and quickest answer was to remove the VHDX’s and reattach them, after that the machines started with no problem!

Hope it helps!