Why cant I sign in to my x box accounts?

I totally understand your frustrations but no worries it's a great improvement that you are able to sign in to the accounts now.

If I may ask, may I know which account was the Forza Horizon 5 game purchased at?

If it's on your account, please sign in to your account on the console, then press the Xbox menu button > go to Personalization > My home Xbox > Then please select Set this account as home Xbox.

Once it's confirmed, sign out from the console and have your son sign in on his account then try to play the game Forza Horizon 5 to see if it works.

Please take your time and let's hope for the best.

Oh you've got nothing to worry! Rest assured that factory reset keep my games and apps will not delete your in-game purchases or saved data progresses as both are permanent to the account where it was acquired.

I understand, have you performed factory reset on both consoles? If not yet, please try to perform the factory reset keep my games and apps on your Xbox One S console > then check if it works.

If it still doesn't work, may I have the exact error message upon attempting to log in to your accounts on your Xbox One S, please?

Hi, thank you for the reply! It will let me sign in to his account on my phone, but when trying to sign in on his x box it comes up with the message "we can't sign you in.try again in a few minutes or check service status in x box assist ( Ox87DD19) it's done this since Friday, and is the same when trying to sign in my my x box account!

Habmve reset mine too and still can't sign in, coming up with different codes as well as the one I mentioned on my sins its also coming up with (0x87DD0017) and this (0x87DD0019)