Hello & Welcome to Just Answer,
I'm Greg and will do my best to assist with this issue today.
Sorry I didn't see your question earlier and to hear of any issue with your phone(s).
To help with this issue, may I ask:
1) Has the device been physically unplugged from power for a period of time, and just recently reconnected?
2) Do you still have the "Operating Instructions" (manual) for this device?
I ask these questions because it "sounds like" some of the "feature" settings may have been lost or changed from the previous settings - when it was working properly.
If you don't still have the manual available, I have a link to the electronic (PDF) version below - that can be viewed on a computer/device, downloaded, saved, and even printed if needed.
Click Here for Manual --> https://business.panasonic.co.uk/communication-solutions/sites/default/eu-files/communication-solutions/files/technical_downloads/KX-FP205E-PFQX2485ZA-English.pdf
According to the table of contents, most of the details about using the Answering Machine starts on page 33 of that manual, with most of the "features" starting on page 36.
I hope this information helps get the device back into a working state.
Please let me know what you find or if you have any more questions about the device.
Cheers, ***** *****