He had dissed off the bell wire between the master and the extension, as folk often do, and in doing so remorovddvthe source of the ring current to the extension.
Not so. The ring voltage is presented across the A and B wires and is therefore present at all extensions.
OP. For devices that expect a ring voltage between the ring wire and the A leg the following faults could be present...
1. Short between the A leg and the ring wire.
2. Disconnected Ring wire.
3. Swapped A and B legs to the extensions.
The only reason the ring wire exists on UK circuits is to prevent bell tinkle.
Modern devices do this by suitable filtering of the ring signal present across the A and B pair such that ring detectors don't respond to inductive EMF.
One fix is to just supply A & B to all extension sockets and fit masters at each.
Edited by Eeeps (Sun 16-Oct-16 19:54:05)