Reversing light not working. new bulb fitted

You need to check that you are getting power at the bulb holder,if not then locate the reverse light switch and bridge it with a split pin across the terminal,s as it,s probably a faulty switch.

I had the same problem with my 2009 308.
I did the same, changed the bulb but no light!
I took it to the service centre and(how embarrassing)they told me that what appears to be a reversing light(the one on the right hand side as you stand at the back of the vehicle) is actually a fog light not a reversing light.
Hope this helps.

The LHS Rear light has the reverse globe in it. The RHS uses the same globe for a fog lamp.
If you want more light (as one light is lousy) you can run some wires into the LHS Housing and hook up
another light/spotlight on the bumper (or off the towbar if you're lucky enough to have one)
Make sure it's only about 10 watts so the system doesn't detect over-current and get sad.
A LED spotlight worked great for me! -spitcake