Humana Medicare refusing to be secondary

I am a 48 year old, disabled on SSDI, and married although I am mid-divorce. I sat next to my husband during open enrollment and watched him sign both of us up for health insurance. (changing from Aetna silver to Aetna bronze plus) He filed for divorce in December, and the divorce mandates that he maintain that health insurance. Additionally, as open enrollment ended before the divorce process started, he can't legally remove me from his insurance until he has a divorce decree in hand since the divorce *he* filed for has that as a stipulation. I have also had my PCP and the pharmacy both successfully bill Aetna as primary this year, so I *know for an absolute fact* that I have Aetna insurance and unless I'm crazy, it's primary just like it's been for a decade.

I also know that because it is spouse employer provided insurance, and I am disabled, that Aetna is primary according to Medicare's own rules.

Because I knew this divorce was impending, I signed up for Humana for the first time this year. I have previously only had standard Medicare A&B without drug coverage. I was like "oh, I'll get the drug deductible out of the way early in the year and get used to how Humana functions." Nope. Not at all.

The pharmacy system is showing that Humana is insisting they are primary. I have called to talk to them, and the rep insisted I don't have Aetna at all, and that I have American Property Casualty as my primary. What even is that? Maybe related to a worker's comp issue from five years ago that was resolved more than four years ago?

I'm not crazy, right? Humana Medicare *must* be secondary?

Also, what would happen if I walked into the pharmacy and let them bill Humana as primary for my prescription? I'm not saying I'm gonna do it, I'm just curious. I've been out of the med for a week, it's $250 on Aetna since I can no longer use manufacturer coupon programs, and if this is a "you can sort out the problem later and pay what is owed, if anything" issue, maybe I just go get it and sort it out later. I really want to stop peeing every 30 minutes and be able to leave my house again.