I first encountered the issue a few days ago on my non-ladder character. It was my first time logging on in quite a while as I’d taken a break from the game, but when I couldn’t sell anything to NPCs. Didn’t think much of it at the time, wasn’t really hurting for gold on that character, no big deal.
Well, now I’m trying to start a new ladder character and I’m still experiencing the bug several days later. I tried quitting the game entirely and restarting, I tried loading into a game by myself, I tried joining other people games, I tried hosting a public game - nothing worked and I still cannot sell anything I pick up. Seems like the only thing I was able to sell was my starting weapon - other than that, I tried selling both consumable items (arrows, bolts, javelins) and durable gear (quilted armor, some random bow I found).
Needless to say, the game is MUCH harder when you can’t sell anything. If my only means of getting gold is picking up gold off the ground, I’m going to have a heck of a time affording potions and scrolls (to say nothing of belts or other starter gear).