DTMF tones recently stopped working on iPhone SE; no changes in carrier, phone, etc. How to fix?

This is actually a pretty common problem.

When you call a number the remote “phone” sends a signal saying the call has been accepted (called “answer supervision” in telephony lingo). Until the network sees that signal it blocks DTMF from the calling number. Sometimes the called number is just slow, so waiting a couple of seconds will fix it.

Other than that usually this is a problem with the system that accepts the calls not answering properly. If it happens with all numbers you call contact your carrier, as something isn’t working right in the network.

And sometimes just hanging up and calling back it will work the 2nd time.

Things that you can try on the off-chance the problem is with your phone is to restart the phone, and reset network settings on the phone. This last step will erase Wi-Fi passwords, but won’t result in any data loss.

If you hear them then contact Verizon tech support and ask to be escalated a higher level.

While I’m pretty sure it isn’t related, is the Mute switch not on Mute?