Trading Post Issues
Its been happening since launch. I’ve reported it at least a dozen times and no fix yet. Best way is to keep restarting your client till it works.
Please try the suggestions in the linked posting. It is possible that the BLTC processes are “stuck” and still loaded in memory from the previous launch of GW2 client (as long as you have not restarted, as restarting the OS removes all processes from memory). Please remove the offending processes from memory as listed in this posting, or reboot the computer.
https://forum-en.gw2archive.eu/forum/support/bugs/Mac-Beta-Trading-Post-Issues/first#post3156901