Getting the same run around as well. Citi has done a good job of making any references to Priority Pass disappear. What little is left (and found via Google) says that you can get an invitation code form the Citi Mobile App that you then submit to the PriorityPass.com website.

However after several calls and being on hold for 1+ hour, Citi representatives have not been able to provide the code or tell me how to get the code from the Citi website or Mobile app.

Prestige is closed to new members, but it sounds like they want to kill off the existing members and/or try not to provide promised benefits. Pretty pathetic.