Can't access Season Pass or Ultimate Team (Xbox One)

After playing a match in Ultimate Team, my game refused to go back to the main menu for several minutes. Eventually, I ended up closing the game. When I turned it back on again, I had been given a message stating that I had disconnected from the game (despite it being over at that point).

After that, I have been completely unable to access Ultimate Team, or open Season Pass. It states that "Connecting to Ultimate Team is not possible", and "Season Pass is currently unavailable".

Whilst I CAN log into the Ultimate Team App, if I attempt to change anything in my active squad, I get the 'An error occurred and changes to your squad cannot be saved' message. Whilst I also can create new squads, I also get the message when I attempt to make one of these squads active (I know there's a workaround involving this, but I can't even get that done to try it out.)