I had the same issue. I ran troubleshooting for the windows store, which seemed to do nothing, but then when accessing the game's store page, it now said "reinstall required" rather than "play".

Reinstalling required of course downloading all 70gb of the game again, and it now works.

The only issue is that the game never uninstalled itself properly, so all the data is still on my harddrive in those ridiculous encrypted folders, and I don't know which folder is the current, working install, and which folder is the broken install.

After working fine for a week my game is now dead again. Haven't changed anything; don't even get the splash screen now.

Just wsappx.exe spinning one core of my CPU and one of my HDDs and nothing.

EDIT: And now the windows store wants me to reinstall the whole game. The "if your game isn't working please run it as administrator and check that your hand drive is big enough" message they've added is honestly insulting.

@Fezix93 This was it! This was the only thing that made it work for my partner! Thank you! We can play now!

Did not even have to reinstall (again) or change permissions, just closed Nahimic 2 and it started working.