You blocked my account and now I can't play Forza Horizon 5 and I can't change my account,...

You can't do anything...once it's linked, it can't be changed:

"Linking a Microsoft account to a PSN account is on a title-by-title basis and permanent. Players have the ability to unlink the Microsoft account to that PSN account, for Forza Horizon 5, but will be constrained to relinking to only that specific and originally linked, Microsoft account."

https://support.forzamotorsport.net/hc/en-us/articles/39144665637651-Forza-Horizon-5-on-PS5-FAQ

Problem solved, I created a new account on microsoft store and xbox app and games Forza Horizon 5 are now running smoothly. I can't use my main account anymore for some reason, but as long as the game runs smoothly it's fine. Thanks for your atention.

I tried other browsers but it didn't help. I want to change settings in my xbox live account because in Forza Horizon 4 I can't see players's car designs. I get message like:"This function blocked in parental's control settigs". But I didnt set on this
setting and my parents didnt set on this setting because they dont have microsoft account.

You know what is weird,

I used to play Forza Horizon 4 on my computer with my brother account. Multiplayer worked fine.

As he got his own PC now, I have created my own Microsoft account and bought the ultimate version of the game.

It seems linked to the change of account and my new GamerTag as I didn't change anything on my computer or my router.

Also, switching to my brother account on my computer is fine, multiplayer works.

I presume it has to do with my new account but please help me, I have paid 100 euros and can't play online.

I have tried to post this twice on the forza Motorsport forum but it says an Admin must check the post before and each time I can't see it. It is like they are refusing to display my need of assistance. Also my ticket at the support is open for 12 days
now without any reply.

I found that I can't sync, get my old data back. But, I found a way to get the forza horizon 4 in my second account! In Microsoft store it says that I can play forza horizon 4,or buy to my own. Does this mean that I have to buy the game? I think no.