It's because the device has tried to get authorization for running the app (a unique, per UDID signature) and has made the assumption that for whatever reason y

It's because the device has tried to get authorization for running the app (a unique, per UDID signature) and has made the assumption that for whatever reason your access has been revoked. That will normally never happen, it's just an odd side effect of whatever this downtime is. People not seeing this just happen to have hit a local cache of some sort and will eventually get it the longer the downtime goes.