Arthur Ravenscroft was thinking very hard :
Most of the sockets are ok (3 lights on the socket testing device)

You do know that those testers are only a rough and very basic test,
don't you?

The continuity of the ring needs to be tested through all three
conductors at the origin of the ring, the earth loop impedance needs to
be checked and the insulation resistance too.

It concerns me, that someone who claims to have extended a ring, has to
come on here asking about such an easily and obvious to sort out issue
as the one you are asking for advice about.