Have a Lumia 640. I was enrolled in the Insider Program and using Windows 10 Mobile. Rolled it back ton Windows 8 with the Windows Device Recovery Tool but left Reset Protection on, apparently.
I tried to find my Recovery Key on my Microsoft Account Devices. It was there, but the instructions had laid out removing the device. I did so and the next screen was a broken link. When I went back to my listed Devices, my phone wasn't listed. Did not receive the recovery key via email either.
Is there another way to get my Recovery Key?