I installed a string of 12 pot lights from Costco and they worked fine for 4 months. Yesterday I flipped the switch, the lights came on and went off immediately. I have power at all the lights, I have bypassed the switch, but no light...and suggestions?
I'm assuming you're using an NCVT. If you "have power" and it doesn't work, you've lost the neutral somewhere.
Check all the connections inside the housings:
Near the bottom of a standard can light there are three screws. Remove them and the entire inner tin-can should pull down out of the ceiling. This provides you access to the junction box that is part of the lamp; where its connections are that you need to inspect.