Accidental Ban?

I have been banned for . . . What!?
After I finished up a assault match on Arena, I have left the lobby to play another game. A few hours later, I went to warzone matchmaking to find this
“At least one player in your fireteam is not permitted to play multiplayer games”
What the heck did I do?
I did not suicide on purpose. I do not team kill.
I just did my regular match?
What did I do!?

I see nothing wrong indicating a reason for the ban, but noticed you have played some griffball, where unintended betrayals can accumulate leading to being booted from a match or being banned for betraying. but I see no reason for your ban.