I saw this when I was lurking the admin chat. They've got a tough road ahead of them since they have so many users subscribed to so many communities on the fediverse. They'd have to unsubscribe and resubscribe to all of them to resume federation with each instance.
We were fortunate enough to have few members and very few subscribed communities when we swapped domains while we were just starting out. So it was no biggie for us.