Not a question, but a solution. I forget the user's name, but he had the same issue as me. MS 'GET' button is greyed out and other functionality of MS programs, like the Xbox app, were not launching. Uninstalled and couldn't reinstall.
Windows 10 and 64 bit OS
I fixed this issue on my PC, by going into the the programs and features app, this is DISTINCTLY different from the apps & features. In the bar on the left side, you can select the link 'View installed Updates'.
I scrolled to the Microsoft Windows part of this window and began to uninstall everything labeled update for MS Windows... all the way to the previous feature update, i.e. 21H2 or whatever it was at the time of writing this. **There are a lot of items that you cannot uninstall here**
After uninstalling those various updates, you will get prompted to reboot. I rebooted, went back to settings / updates and security, and started checking for updates. It found everything I uninstalled and reinstalled it. After a few rounds of reboots and checking for updates, I was able to go into the MS Store and the 'GET' button was restored.
If you are uncomfortable doing the above, you should make backups of data or talk to a local IT person.