Why won’t my Xbox series x connect to xbox live when trying to playing Xbox 360 games?

Last week, I tried to play black ops 2 because all the servers got fixed but when I tried to connect, I get an error stating my console will not connect to Xbox live. I know it’s not my internet because I can play my other games online. I’ve looked at other forums and I’ve tried everything they have suggested. I power cycled my system, changed the the DNS, cleared the ALT MAC. Nothing has worked. The last resort was deleting the 360 storage. I deleted it but when I load up a game, for example Dead Space 2 ( a game I have completed multiple times so I know there is a save file) my Xbox 360 Info will not load. I have tons of Xbox 360 games I have beaten on my console but now that I deleted it and my info being unable to load, I am furious. The Microsoft employees obviously do not care because there has been no solution or fix. Some of the solutions I stated above have worked for some but other people are still having the same issue. Nothing was wrong with playing my old 360 games, I literally played 3 weeks ago with some friends but now nothing works and it’s quite annoying. I do not know what else to do

:)