PinePhone keyboard tones

[KC9UDX]

I think you might already know this but I want to stress it: you won't be able to hear DTMF on your ends. So it's very hard to know if DTMF is actually working. Sone remote systems (the other end of your call) just don't like the tones produced by mobile phones for some reason. (Usually the timing, I think.)

So (maybe you already did) make sure you try different systems (calling different numbers).