Hello & Welcome to Just Answer,
Sorry to hear of any issue you are having with your phones.
May I ask:
1) The AGE of this system?
2) WHEN this issue first began (has it worked in the past and then quit working)?
3) When you TRY to use those key presses, do you LISTEN and hear any "tone", or perhaps a "clicking"?
4) Did you find ANYTHING in the instructions at all, that might relate to this issue?
I see it has been a few days and I just wanted to follow up to see if you have any more questions concerning this issue or if the issue was resolved.
I look forward to any further questions or results that you may have.
Thanks, ***** *****--. .-(im)