For me on win 10 then recently win 11 I get that error every single time with vm workstation 16.2+.
I go back to 16.1.2 and all is well.
From the best of my recollection:
I am mounting to the host OS from the file>map virtual disk on the main screen.
It appear to see the two partitions (GPT) and I select the large one as always. Then it shows me the "mounted" info box but it says "size unknown" and will not assign a drive letter.
Any ideas from anyone or am I stuck on 16.1.2 forever?
Thanks