BT Synergy 4100 phone will not connect to base?

Two of my handsets do not work when trying to answer a call. When the phone rings pressing the green button to answer does not work. The phone continues to ring. But the base works fine. Does anyone know how I can overcome this.
Thanks

AS
June 2014

One of the handsets work and the other kept saying register. Despite trying to register, putting in the pin 0000, and pressing the page button on the charging unit, it still kept saying register. So after reading Jock 157's answer, I tried it - unplug mains charger, plug it back with page button depressed, then do a registration on the faulty one again and then suddenly it was OK.

Joan Guyll
March 2014

how many handsets do u have connected if more than five it will not register
if this is not the case lift the main base unit and remove the power plug underneath also the phone line hold the find button on the base and replace the power lead whilst holding the button u will hear three set of bleeps release the button at the third set have all your handsets with u replace phone line all will revert to base 1 then follow reregistering hand sets should work mine did good luck if this dont work bt have a free help line on 0800 145 6789 but u will need an old plug in phone at hand to talk to them as u will go off line as soon as u unplug the mains lead from ur 4100 base

jock 157
April 2008