Bluetooth headphones automatically reduce sound to nothing on iPhone 11
I recently purchased an iPhone 11 and then some Bluetooth headphones that plug in to the iPhone. All worked fine the first day I used them, but now when I plug in the headphones the iPhone volume automatically reduces to nothing and it won’t change when I try to increase it (I only get sound for a fraction of a second and then it goes back to nothing). Incidentally the sound adjusts normally and works fine without the headphones plugged in. So ultimately I cannot use the headphones at all. Can anyone help as to how to fix this?
iPhone 11, iOS 15