I haven't been able to use multiplayer on Forza 5 or Horizon 2 for months.

I’m new to gaming and very confused. I’ve done all the troubleshooting through Xbox and nothing has worked. Any advice greatly appreciate. I even bought this stupid driving wheel…

A daft question, but do you have Gold membership for Xbox live?

Has it expired? You may have changed your bank and if your on a rolling membership, payment may have not been taken, and membership not continued.

Also, I notice your not even drivel level 1. You need to play through the first few races first. That will enable you to enter the main menu, and go online.