Three prior auth denials for a CPAP and I'm exhausted - anyone actually win this fight?

I was diagnosed with moderate sleep apnea after a sleep study my doctor ordered. My sleep specialist prescribed a CPAP. Seems straightforward, right? I've now had three prior authorization requests denied over the past six weeks. The denial reasons have actually changed each time, which is its own special kind of infuriating. First it was "not medically necessary." Then it was "documentation insufficient." Now the third one says I need to first try "positional therapy" for 30 days, which my sleep specialist specifically said was not appropriate for my severity level and documented that in the chart.

Every denial adds more paperwork and another two-week wait. I'm sleeping terribly, I'm falling asleep at my desk, and my doctor is annoyed because she keeps having to draft new letters. The CPAP itself costs like $650 retail. I've probably spent more than that in my own time dealing with this. I know this sounds dramatic but I'm starting to feel like they just keep making up new reasons to stall until I give up.

Has anyone actually gotten a CPAP pre-auth approved after multiple denials? Is there a specific argument or approach that worked? I have a second-level internal appeal available but I don't know if it'll just be another form rejection.