Yeah, I already have my Nexus card, just trying to add APEC. I've emailed multiple times asking why I cant get a Phoenix interview, and I just get the boilerplate that I need to schedule online. I tried to do a interview on arrival like they do with global entry in San Francisco, and after doing the interview, they told me that since I have a Nexus card, they couldn't add the APEC to my account. After trying for 3 hours, I gave up. Its been a battle.
See attached the photo showing my Nexus, conditionally approved APEC, but then the only scheduling sites that show up at NEXUS centers.