The paper trade on two of my villagers is stuck with a red "X" for the trade of Paper so I cannot get Emeralds for for paper at any price.

I found the problem. Although I can trade with the the Lectern missing. The trades will not reset. I put one in and it instantly reset. I was currently using my one lectern on the station I was using to pick a good starting combination of trades before I did the first trade. I was trapped with it on a Mending book and it had to wait until I had enough to lock in that trade.