So I've set up a nice community server, where we've built a town. We've included a market, planning to use the trade signs that are implemented in the essentials plugin. I'm trying to sell iron. However, everytime i put ANY variation on the word Iron Ingot, even the item id, it pops up with a message saying that it's not recognized or that the line 3 is invalid. Does anyone know what's causing this or how to fix it? Screenshot below.