Medicare just denied the rental-to-purchase conversion on my CPAP after 13 months of "compliance proven" use. what is going on and how do I fight this?

genuinely confused and hoping someone here has been through this. quick background: im 71, diagnosed with moderate OSA in april 2025 with an AHI of 22, sleep doc prescribed a ResMed AirSense 11 with a heated humidifier. Medicare Part B covers DME as a 13-month rental, then it converts to purchase and the device becomes mine. the DME company (a regional outfit, not one of the big national ones) explained the rules upfront. i hit 100% compliance for the trial period (4+ hours a night, 70%+ of nights, in the first 90 days). after that i kept the modem plugged in and the data going up to the cloud the whole 13 months. my last 30-day average is 6.8 hours a night.

so i call Medicare last week thinking the rental period is up and the machine is mine. nope. i get a denial letter that says the supplier submitted the conversion claim and Medicare denied it as "not medically necessary, equipment no longer required" because they want a recent sleep evaluation. wait what. nobody told me at any point in 13 months that i would need a NEW sleep eval at month 12 to get to keep using a machine that was already prescribed, already approved, and that the data shows im using every single night.

i called the supplier and they basically said "yeah this happens sometimes, you have to appeal." i called my sleep doc and they said "you can come in for a re-evaluation but its $340 cash because Medicare wont pay for a redundant visit." i called 1-800-MEDICARE and the rep i got could not explain the denial reason in any way that made sense.

has anyone successfully appealed a Medicare CPAP conversion denial? what specifically did you submit? am i supposed to be doing a face-to-face encounter at month 12 that nobody at the DME or the doctors office bothered to tell me about? the machine works, im healthy because of it, and now im looking at either paying $1,400 cash to buy a machine i already "rented" or starting a redetermination process i dont understand. any guidance appreciated. my wife is convinced this is a billing code error and not a real denial but the letter sure looks real.