Just got a Series X and Game Pass. I played on PS4 since launch day and on Stadia for the past year. I wanted to see how things are on the Xbox side. Unfortunately, I keep getting kicked so I have no idea.
Is there a specific error message that you are receiving?
I wanted to get to Eastmarch so I could the 2x XP buff for a new toon. I get the "May be a long load time" message when I tried to go between zones. Then after a minute, maybe less, I would get booted to the title screen and was told to check my internet connection. My internet isn't a problem because I could login and play on Stadia right before that.
One thing I just thought of was that I was playing on GamePass through the Cloud without downloading the game. I'll have to look into that.