Can someone please tell my why my new HID bulbs don't work?

The reason why I bought new HID bulbs was because my left headlight wouldn't turn on at times and I was advised to buy new bulbs from here. Now that I installed the new bulbs, both headlights don't work. I reinstalled them a couple of times to check if they were tightened enough. Later on I put on my old HID bulbs and now both of them DON'T work. They worked fine today until I put them back on. Can someone please clear things up because I am really confused now.

Don't listen to random people on this forum, most like to rice out cars.

But to clarify, the old bulbs work and the new ones do not?

^^^
Old bulbs DID work today now they don't work after I tried them on again since the new ones didn't work also.

I caught my error and edited it on the first post... they both DON'T work. Sorry for the confusion.

Switch the plug around. The harness that the bulbs go into. Not the separate leads(positive and negative) but the plug that goes into the ballast. Unplug it and plug it in the exact opposite way.

Thats pretty much the only solution I can think of without actually seeing whats going on.

Like was stated above, also check the fuse. You might have blown the fuse when trying a bulb in backwards.

I'll check the plugs again tomorrow since its dark right now. I'll get back to you guys tomorrow.

I rechecked everything... The wires, connections and all that... I'm starting to think it is my ballasts with the problem. They seem to lived up their life because when I turn them on they don't make that humming sound they used to when they used to work.

Try new ballasts then, best bet. What brand did you have originally? How long were they on the vehicle?

had the same problem i took every thing out and just re did it. none of this unplug one and plug back in but mine work fine now:)

I'm still thinking about either getting a whole new HID kit or some ballasts. I don't want to waste my money to find out its the bulbs lol.

the brand of HIDs I used were called zer0 racing. I had them for about 4 years now.