Immediately "offline" after startup - no log of server attempting to start at all.

This morning, I attempted to boot my server. It's a small vanilla thing, something I'm running to help my debate team relearn the game before we do a deepdive into intense modding. It didn't boot, which - alright, sometimes servers crash, and while that's really frustrating from the front of a 16 minute queue, life happens.

Looking at my logs, however, I don't see any evidence that the server even attempted to boot - it just has one of my players being kicked for a timeout (and, of course, the server shutting because a three minute timeout isn't nearly enough time to get a player back online), and then nothing.

Can anyone explain what is going on? I'd be thoroughly shocked if three players playing normally (the most resource intensive thing on the server is probably either the like 60 tracks I laid last night or just an ordinary nether portal) made the server so completely unplayable, and while I could probably set up on of my broken old laptops as a dedicated server, that sounds like a pain, and so I'd really like to be able to use Aternos' service.