i have the same issue, please god you get an answer, its driving me mad!!!! i was told to check the earth cable for the lights, but mine already has a second earth running straight off the bulb connector.
Get a multimeter and check the bullets are giving power out. If they are, check connections and earth, if they aren't check fuse, and then it could be dodgy cable or maybe the switch
I had the same a little while ago. Make sure you arent swapping the earth and one of the terminals, I know on mine it wasnt clear which was which. Mine works fine now, although for about 2 weeks I had both the wrong way as I went for a cuppa before I took the light out, then did the wrong one!