I don't know if it's still the case but at some point in time villagers were unable to interact with workstations if they didn't have at least 2 blocks to move around in, I cant tell if your villagers are blocked in to just one blocks space or if they can move back and forth side ways.
If they are blocked in then try giving them an extra space to move in.
Doesnt look like that made any difference for me. But thats interesting though!
I have watched some videos on making theese trading halls and they only made it so that the villagers stays on one block. So i dont think thats the issue here... :/