Cant download any game nor start any from xbox beta pc app.

Hello there, this issue has happened to me multiple times as well. The way I fixed it is by Task Manager>Advanced and then find where is shows either the game and the xbox app and make sure to end it. If that doesn’t work, I’ll try to find a way to fix
it.

I don't think you actually need the Xbox beta app to launch any game? The app is useful for checking the Xbox Game Pass for PC catalog, but you can also download any games via the Microsoft Store without the Xbox beta app. And the app doesn't need to run
in the background when you're playing Microsoft Store games on your PC

Hi Yannis,

In order to install this game or any game from the Microsoft Store App, you will need to ensure your Windows 10 device is on a 1903 OS build or greater (Current 1909). The easiest way to ensure your PC is ready to go for this game and any other game
that comes to Game Pass for PC is to install the Xbox (Beta) App with the steps posted here. This will force the PC to install
an OS version that can run all Game Pass for PC games and allow users to easily find them inside the Xbox (Beta) App.

Let us know if you have the most recent OS build for Windows and the Xbox (Beta) App and try installing the game from the app as well.

Flight Simulator 2020 I open it and at the start it says "Press any key to start" and I press a key and it just flashes and says the same message again and it just keeps happening no matter what key I press or how many times I keep trying.

If you have downloaded the game with Xbox/PC game pass you need to download the Xbox (Beta) app. I downloaded and launched from the app and it worked no problem.

Have you tried downloading it from the Xbox (beta) app? If you don't have the app, you can download it from https://www.xbox.com/xbox-game-pass/pc-games?xr=shellnav
(Just press Get Started)