IPhone does not generate DTMF tones
Quite often after I have dialed the number and dealing with voice menu where I need to push buttons for various options, the phone fails to generate the tones. I press any number, the screen flashes briefly, but no tone is generated. Usually I am able to "fix" the problem by actions like turning on and off the speaker, or hiding and restoring the keypad - then suddenly it starts working and pushing the buttons generates the tones.
This is iOS 16.0 on iPhone 11 Pro Max
iPhone 11 Pro Max