This is the most common problem we come across in support is an un switched BC | B22 | Bayonet cap lampholder not working.
Its almost impossible for a lampholder to not work as its all solid brass construction with no switches, electronics to go wrong.
For some reason the manufacturer makes the lampholder so it "could" be put together incorrectly.
if your lampholder is not working please see the images below and ensure your lampholder looks the same, this will solve 99.9% of lampholder not working support questions.
This is bases on power getting to the lampholder.
The easiest way to check the alignment is by looking at the top of the lampholder as shown on the left hand picture.
If you are still having problems with the light fitting not working please contact us using the ?help button at the bottom of the screen.