Hello & Welcome to Just Answer,
Sorry to hear of any trouble you are having.
It sounds like you have a KX-TGF345 system - since you mentioned having FIVE handsets (that's how the last number of the model is determined).
So can you VERIFY that ONLY ONE of the cordless handsets does not appear to be giving you sound, from the callers or dial tone?
If so, may I ask if you have tried using the SP-PHONE button on the handset - to try to listen for the dial tone (or conversation)?
NOTE: that is the lower-left button on the handset.
Please let me know if you hear anything when using that button.
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, ***** *****