Can't play games from family group even though I could recently.

Hi FilipLadan

Yes, the fact that you are playing on PC does change the overall answer because sharing games doesn't work the same way and the troubleshooting is different for that error code depending on what platform you play on. The support article presented earlier
by an Xbox Ambassador is only for help with that error code on the Xbox One console. I'm moving the thread to the Xbox on Windows/PC gaming section to reflect that you play on PC for easier recognition.

The Microsoft Store for Windows has been known to give that error if the time zone settings are not set to automatic.

1. Open Settings.
2. Click on Time & Language.
3. Click on Date & time.
4. Turn on the Set time zone automatically toggle switch as well as the Set time automatically switch.
   

You should also try logging out from the Microsoft Store and then try logging back in with the account that owns the games and make sure the PC you are using is set up for

offline permissions.

Did the owner of the digital games you now cannot play change their Home Xbox setting on their account? Because you cant play games that people on your family accounts own unless either you are on the home xbox of the account with the game, or the person
who owns the game is logged onto the xbox at the time you play

I'm playing on PC, not Xbox. I just use the Xbox app to access the games that I have on windows 10 (and yes they are all bought from the Microsoft store.) if that changes the overall answer.

But if that's the case then how was I able to play the games then?

I have, all 9 of them, multiple times. The last option is to buy it but that's only if everything else fails.

Have you tried the solutions posted for that particular error code yet? https://beta.support.xbox.com/help/errors/error-code-0x803F8001

If so, what other messages/errors did you receive?