I'm sorry I can't be any more helpful than this, but I would try replacing the fuse, just in case. I had the exact same problem with my 2006 Hyundai Tiburon except I had my phone charger plugged into it.
And the fuse was still good, but I replaced it anyway with one of the spares they should have given you in the fuse box, and after that it worked just fine.
Or it might be that the power converter you used might have had too much electrical current running through it and it might have done some damage to it.
Well I hope this helped!!!
If you still can't figure out what's wrong with it, try finding a new power outlet for your car on Ebay or something. You could probably find one for, I'd say around $5 - $15.
=D