Hello & Welcome to Just Answer,
Sorry to hear of any issue you are having with your phones.
To help you with this issue, may I ask:
1) What phone service provider (phone company) you have for this phone line?
2) Do the phones work properly - other than not being able to take incoming messages?
3) If you have ANY other devices (phones, fax, alarm system, etc.) attached to this same phone line (not part of the MAIN system), and if so, are they working properly?
4) Do you have another phone line available (such as a cell phone or neighbor/friend's phone) that you can use to call your Panasonic number, and TEST what is heard (in the calling phone)? If so, please place that call, and let it ring a number of times (up to 10) and see what is heard - in the calling phone).