iPhone 15 iOS 17.2.1 ringer volume

If your phone is in a case, check to make sure it the same issue occurs when the phone isn't in a case.

If your phone is not in a case, make an appointment to have your device examined, as it may be a hardware failure:

Genius Bar Reservation and Apple Support Options - Apple

Alternatively, contact Apple Support directly:

Contact - Official Apple Support

I have the same issue, and it's quite annoying. I switched from Android recently, and tomorrow I'm going to return the phone to the store.

Ive lost the ability to use the increase volume button at all….decrease volume works fine but increase volume has stopped working, so I cant increase volume while in apps/or to adjust notification sounds and can no longer do screenshots.