According to users who have shared their concerns, following the update, they are now seeing a “No Service” message at the top of their iPhone’s display. It doesn’t seem to be iPhone specific either because users with all different iPhone models are reporting that they are experiencing this problem.
There also doesn’t seem to be any kind of universal fix as some users have luck with some methods, while others can’t get it to work for them. Apple hasn’t officially come forward to say anything yet, so we’re not sure if they know about it. However, the company does have a support document that tells users what to do if they encounter a “No Service” message.
They have also recommended that users check for a carrier update which could potentially fix the problem as well. Either way, there is no telling how widespread this problem is, but if you haven’t updated to iOS 14.7.1 yet, maybe holding off first while this gets sorted might be a good idea.