I had this same problem too... at first I thought I'd updated by iPhone to a newer version of iOS than that supported by my Xcode install, but it turned out not to be the problem (14.4).
In the end I just restarted my phone and everything worked fine after that.
Not exactly a scientific solution, but sometimes switching it on and off again really is the best solution... 🤷♂️
Topic:
Developer Tools & Services
SubTopic:
Xcode
Tags: