Its not a version info. Our version isnt really an indication anymore of if its up to date with vanilla since we diverged in features and now pull in patches piece meal.
In all liklihood they moved to a whitelist server or a server that blocks a large portion of the fediverse, including us. So they arent able to migrate because the server they are migrating to likely blocked them from doing so.
The server they moved to doesnt publicly list blocks, which is usually a good indication they have a massive block list they want to hide so as not to discourage new users.
@arnaduga @arnaduga Have fun!
You can use the move feature which'll mark this account as 'has moved!' and link to the new place.