When left-clicking on villagers who trade, the trading box will pop up for a split second before disappearing, or not appear at all. This was occurring for all villagers in a plains village, making it impossible for me to trade with them. I tried leaving and reentering the server, as well as leaving and returning to the area, but the issue persisted. And it happened regardless of whether I had anything in my hand when left-clicking or not. I could, however, trade with a wandering villager with no problem.