Well… that’s how it should work.
The AppOfflineError part could mean that the Anvil server is down.
The Connection to server failed part could mean that the client can’t reach the server.
Usually, when you get this error, there is a connection problem, it has nothing to do with Anvil.
The connection between the client and the server hops many times and there are many points of failure.
Perhaps Anvil could do better to improve the description of the error in some cases, but when you deal with long distance (and also short distance) connections, you always need to manage the random failures, because you will always have random failures.