Connected to East Coast USA.
I also just tried the log into MSFS “NOT AS” Administrator trick as that worked in the past, but not now.
Any how, I thought I had nailed it, & it was on me.
When MSFS was released the crazed early adopters figured out that if they set their Win10 Region to a 1st past the post country, they would get MSFS earlier then their actual location.
I went with Samoa & had forgotten that.
I have just changed Win10 Region to USA & the "XBox Game Pass Not Available in Your Region " message in Xbox, has gone.
However, “Buy/Download” still greyed out in Market Place.
Head scratcher.
TG