Exactly the same problem here. When I installed iOS 15 on my iPhone 12 Pro, this started to happen, and I don't have any profile to accept on device management. This is very frustrating.

It just hit me. I used to have a paying account and don’t anymore. Could that have anything to do with it?

I contacted Apple developer support and it was never helpful. They all said the usual stuff and ended up sending me to Apple developer forum. Which is ridiculously ironic and funny. :( they told me we don’t need a paying account to test our apps on physical devices. This is probably the most frustrated I’ve ever been with Apple. :((((

I eventually gave up and payed for a subscription and obviously it worked. But I was told by Apple support that a paying subscription is not mandatory for this to work. But they didn’t help me further because I didn’t have a paying subscription. 😅 oh well…