I’m having the same problem, I can browse and purchase items just fine. But when i try to sell, the page loads forever.
EDIT: So after googling some more, I found clearing my internet browser cache did the trick. Something about TP using the browser cache.
https://forum-en.gw2archive.eu/forum/game/bltc/Unable-to-sell-and-see-stats-on-trading-post
(edited by Nate.7806)