cant buy anything in Hall of Monuments
It is broken since forever now. Devs too busy with the expansion.
A major and complicated bug set in a few months back. It’s closed whilst the fix is being sorted
https://forum-en.gw2archive.eu/forum/support/bugs/Instant-God-Walking-Amongst-Mere-Mortals/first
To be more specific, a bug in a patch a while back accidentally granted some players achievements through the Hall of Monuments that they didn’t earn. So to address this, the devs disabled access to the Hall of Monuments temporarily, only recently reinstating access to the location but not the vendor inside. They did make a statement that they were working on a fix but said it would take a while as it’s a complicated issue.