Why can’t I update my iPhone to iOS 15.7.1 ?

iPhone XR , running iOS 15.6.1, with 12.25 available GB. When I tried to connect it my laptop (Monterey 12.6), which was 1 option that was suggested, that connection seems "inconsistent" (flashing window asking if I trust my laptop).

Which iPhone do you have?

I have a 12 mini and get an error every time. I’ve cleared space, and restarted, tried on wifi and cell. It finishes downloading and then says “an error has occurred downloading 15.7.1