We had been away a month and now can't get the phone to answer if we have carried it away from the base i.e. down the garden. I have taken all 3 handsets off their bases for 12 hrs but no help. It is a BT SYNERGY 4500 any ideas
phones 3-4 years old
Then the rechargebable batteries have almost certainly passed their useful life, two years is normally the limit.
If they are AAA rechargeables, they are cheap and plentiful to replace.
You can prove it by putting in a couple of ordinary batteries in one handset, but do not put the phone on its base, as the batteries will leak and may explode.
If the handset works, then take the batteries out, and order replacement rechargeables for all of the handsets.