Phonak Dect II

I bought a Phonak Dect II that was previously owned, for my mom.
I keep getting the message, "no base station ".
The Phonak base is plugged into a working phone line.
The Phonak base has power going to it.
If I press the “pair” button on the back, nothing happens.
I thought maybe I could de-register and re-register the phone, but there are no instructions that address this, apart from a mention that the phone comes with a 0000 pin number, where they are paired at the factory.
Thank you in advance.

If it’s pre Marvel it will work, after that it is not compatible.

Any lights on the base? Sounds dead.