Sometimes Roon gets confused, in particular if connection to the regular server failed. Then it thinks that the server it finds now is a new server. (The identification of a server is apparently not an exact science and depends on a range of factors).
Since your license can only activate one server at any one time, it asks you to transfer the license to the „new“ server, even though the „new“ server is physically the same one.
Just connect to this „new“ server and everything should be fine.
Side note: In the last update, Roon Labs tried to make this flow more reassuring and less scary, so now to says, „Don’t worry, your music and settings are safe“, but perhaps it’s not yet reassuring enough, so I mention this here as feedback 