My iPhone’s microphone isn’t working in few apps

Goto settings on the iPhone and select the app/s that are allowing access to the microphone. There should be an enable setting or check mark that should allow access to microphone. Such as GarageBand, iMovie and others. Do this other apps have issues with microphone, check those settings as well.

By default some third party apps will not get microphone access by default. A quick check will help determine if it’s a configurable issue or a hardware one.

If the mic works with GarageBand but not others, it’s either the config or the app needs a update.