To be clear this isnt a mastodon problem, but some sort of problem that occured in migration of our servers. We have some fixes in line and should have it resolved soon I hope.
In the meantime one thing you could do is export your following list and import at the new location. This will alert people you follow them.
Also keep in mind even once fixed expect to loose a **large** portion of your following (typically double digit percentages). This is because as a server with one of the largest footprints many of your followers often dont federate with other servers. So expect a noticeable loss as a result of that which is typical even when its working.