not sure if RE or Empyrion, but I play RE so...

when launched in Steam offline mode (internet was down), all my saves were labelled as missing something. Attempt to load recent save resulted in internal error. Attempt to continue anyway froze the game.

Once internet was back on, the very same save file loaded normally as if nothing happened.

I am not sure why, but I am sure that at least couple versions back it was possible to play offline.