This is quite worrying me now. I have a number of recording merges lined up. I hope there is a way of rebuilding that data once the AcoustID server comes back on line. I am fairly sure I am seeing a lot of missing fingerprints on other tracks.
Even just on a human level - is the guy running the server okay? Has anyone heard from him to check he is healthy and happy? Loosing a resource like AcoustID would be inconvenient, but I hope nothing has happened to @lukz as this is now a long time with a lot of silence.
I have never talked to the man, but wish him all the best with whatever he is going through.