the TP? it’s their clever way to tell you you’re selling too quickly. you’re only allowed like 10 sales per minute. if you go above that: error.
fun bug: if you keep trying to sell waiting for the error to go away, it won’t. with the last update, you have to do nothing and stop playing gw2 for a minute before you can sell again. I guess it’s Anet’s way of telling us to stop playing so much.