Xbox app for PC won't launch Forza Horizon 5, won't download some games, very slow download...

I got a new desktop with i9, RTX 3070 Ti, 32 gb RAM. I did all the Windows upgrades. I downloaded Xbox app for PC. I am a gamepass ultimate subscriber. I also own Forza Horizon 5 ultimate (purchased from Windows store). Firstly, some games will not install. Secondly, the two games I got to install (Forza Horizon 5 and Hitman 3) took hours and hours to download. Hitman 3 will launch but only after waiting 2 minutes after I hit the launch button. Forza Horizon 5 will not load at all.

I also have a laptop which I've played games via the Xbox app for the last year. Games will download and launch from my laptop. But there is something seriously wrong with the Xbox app on my new desktop.

I have repaired, uninstalled and reinstalled the Xbox app but to no avail.

:)