Now, I know this may seem odd because it seems like it’s meant to be literal, HOWEVER I was the only one on the server and I wasn’t trying to “smelt” a pufferfish nor was it anywhere near my auto smelter. The error I got was “Couldn’t smelt 1 pufferfish because there is no smelting recipe”. Now, at first I was thinking “well that’s just self explanatory” but it’s such an off the wall issue I had to look it up to no avail. Is this some kind of inside joke or was the server trying to fetch a pufferfish smelting recipe for some reason?
This doesn’t sound like a vanilla message, and it probably was sent by a plugin on your server. Can you post a list of installed plugins?