I can't connect to internet on Xbox 360 and with Xbox 360 backwards compatibility on Xbox One

Hello, I always liked to play some backwards compatibility Xbox 360 games on my Xbox One S.

Unfortunately, it is not possible anymore from a couple of months and I didn't do anything to my "internet" but I did reset my Xbox One S because of a couple of issues (which didn't even get solved).

I always used it and it worked perfectly fine, now if I start a backwards compatible Xbox 360 game it will start completely fine but it won't download any Xbox 360 file (I'm talking about the "collecting Xbox 360 info" screen) and I won't be able to download any profile because it wil give me an error message which says:"Can't connect to Xbox Live" even though my Xbox One is connected to Xbox Live and works perfectly fine.

I even tried connecting to Xbox Live from my Xbox 360 E and that gave me the same error.

My only guess is that the internet provider changed something and I'm no longer able to connect to Xbox Live using something like a 360 internet "thing".

I can't even touch the WiFi router because I have always used my mobile phone as a hotspot.

If someone knows how to solve this I would really jump from the happiness, but I doubt since I tried switching amd changing lots of different stuff from the router menù on my Android device (Samsung Galaxy A71 and I even tried with a Samsung S10).

Thanks.

:)