Can't play Forza Horizon 4 online

Dear all,

I am having issues to play Forza Horizon 4 online whereas it used to work properly a couple of days ago.

I have tried every single possible solution to solve my problem but nothing seems to work.

To sum-up:

- I used to share my account with my brother where I owned Forza Horizon 4 and online has been working properly

- I have created my own Microsoft account and bought Game pass for 3 months as well as Xbox live gold for 1 month.

- I am using the right account on Windows and everything seems properly synchronized.

However I can't join any ingame multiplayer session.

I have checked my network and saw that I had troubles with Teredo.

I have solve that and Teredo is fine showing qualified, network "managed" and all Connectivity stuff is OK whether it is in Windows parameters or in the Xbox app.

I am not having any other issue with my internet or my router. I mean everything works fine.

I have tried and checked everything:

- services in windows

- cmd

- ports are open in my router

- ipv6 OK

And so on.

I am about to give up guys, I need your help as everything seem perfectly fine.

Could you please give me a helping hand?

Thanks in advance.

:)