Originally Posted by tel the sky
Yes, I've already tried that link and it does not let me sign in with the specially supplied username and pw that I paid for a few years ago.

Any idea where I can get programming info (not user info) for a Panasonic KX TS4200?

HERE try this ,if you can virus scan it, just got off internet.
https://headsetplus.com/PDF/KXTS4200.pdf.