I have finally fixed this issue. It was because danish letter Ø in associated domains, I have removed it and now it works for ios 15. I will report ios 15 issue, such as ios15 cant handle domains which has these special chars, but it should be possible such as site domain can have it.

also if app is pushed to TestFlight, it's not possible to install to device with ios15, I afraid it will not work on ios 15 if it's pushed to store

Please help with that, I have the same issue!

I have the same issue, please help us

I still have this issue macOS 11 iOS 14