I had a similar problem when I installed led tail lights on my Jeep wrangler. The turn signal flasher had to be upgraded to a Heavy duty type flasher. The original flasher depends on resistance to heat up the elements of the flasher and cause it to flash. The led lights do not create this level of resistance, and therefore will not flash thru the original flasher. Get a heavy duty flasher at NAPA or a truck shop, plug it in and your problem is solved. Good luck