Gigaset A420 issue

Hello,

After unplugging our landline phone (Gigaset A420) about 7 years ago, we need it again. So I take the phone out, plug it back into the power socket and into our SFR box (socket "Tel1"), but nothing happens.

I think the phone is out of charge but the base doesn’t seem to be charging. It lights up briefly to display "BASE" and the screen turns off; I just have time to see the empty battery icon in the upper right corner, but preceded by a small lightning bolt (which remains after now 8 hours with no change in the displayed battery level). The phone buttons make noise (remnants from the batteries?), but nothing shows up when I press menu or anything else, the screen is blank. I removed the original rechargeable batteries and charged them separately. But after putting them back in the phone after several hours, the problem persists… I can’t try anything on the handset side since I can’t access the menu etc because I only have access to the screen for a second.

I tried to call myself, the Gigaset doesn’t ring. And when I place the phone on the base, it used to make a sound, but not anymore?

The electrical plug of the base is very strange (one round end and one regular plug end) I wouldn’t even know where to buy another one to test the power supply, to be honest. That said, when I press the unique button on the base, there is a noise (that takes some time to come), so I suppose the power supply is working.

I really don’t understand where this is coming from? Do you have any ideas?

Thank you very much!