Multiplay on age of empires 2 grayed out

Hi there,

I got the following problem: The multiplayer option on age of empires 2 is grayed out and cannot be activeted. It belongs to my sons account. I only created that account it because of that game. There is an "error message" already at the beginning saying
that settings in the account would restrict some of the features of the game. It does not say anything specific, very general message that is not helpful at all.

We play on Windows 10.

What I tried already:

1. Remove every possible restriction on his XBox account

2. Re-install everything

3. Remove every possible restriction on his Microsoft account

I googled a lot about that problem but only found other people with the same problem but no solution.

Everything is connected (XBox account, Microsoft account and the game) but it is not working. I waited 40 minutes to get a call from the XBox support and had to listen to 10 minutes of "commercials" .... but the person from the support team was not able
to help me and asked me to call the "Developer" of the game (btw it is XBog Game Studios...no comment) but was not able to give me any contact information.

Can anybody advice how to get out of this problem? I would really like to play age of empires II with my son ... *cry*

:)