Friend is unable to join at some times but not others and MCC won't let him join my lobby

[how horrifying]

Me and my friend have been having issues with the co-op function in the MCC. For some reason the option to join me is grayed out and when he tries to do so it either says "Your attempt to join this player has failed. Please try again." or "This user can't be joined because you are not following this user or they are not following you." depending on if my invite settings are set to friends only or invite only.
I can join his lobby just fine and he can designate me as the lobby leader, its just that he can't join mine at all. This used to not be a problem until recently, although I don't remember the date that it actually started. We are friends on steam. Whether I or him are the party leader we are most of the time unable to just start a mission. We will start the countdown timer which will then stop at 0 and not do anything. This issue happens across more than one game. Other times it will countdown as normal and start.

We have:

• Reset or had windows fix the xbox networking. (My NAT Type is Moderate and my Server connectivity is listed as connected)
  
• Verified integrity of game files (he had some missing but the issue persisted after he re downloaded).
  
• Restarted Computers.
  
• I have tried changing my invite method from friends only to list.
  
• tried to have him join my lobby from both steam invite and in game invite.
  
• I have turned relays off.
  These problems are intermittent. But every time we play we have to do something. Sometimes restarting our PC's and resetting or asking windows to fix the xbox networking issues will work, sometimes it doesn't and we give up. I would be real appreciative of any who could help us out.

[heof1letter]

This isn't a PC/Steam thing, it's an MCC/Xbox thing 😕
This will happen on Xboxes (One and Series) as well, MCC will just decide "No FU, you can't join this lobby today"

Restarting the system, or changing party settings usually doesn't do anything, but restarting MCC will sometimes help. Sometimes it will help if you enter matchmaking, then exit and try again. If it's just the two of you, the best thing to do is have you join him and transfer party leader. I play MCC a lot, and working around the issue is about all you can do, there's no escaping the fact that this game was made by 343i 😑

[how horrifying]

heof1letter님이 먼저 게시:

This isn't a PC/Steam thing, it's an MCC/Xbox thing 😕
This will happen on Xboxes (One and Series) as well, MCC will just decide "No FU, you can't join this lobby today"

Restarting the system, or changing party settings usually doesn't do anything, but restarting MCC will sometimes help. Sometimes it will help if you enter matchmaking, then exit and try again. If it's just the two of you, the best thing to do is have you join him and transfer party leader. I play MCC a lot, and working around the issue is about all you can do, there's no escaping the fact that this game was made by 343i 😑

Well I appreciate the help anyways. I know 343 is only one company and the MCC is a big project, but you think they would have ironed out these flaws by now.