I agree with Grinder on this. LED bulbs draw very little amps. Some as low as .45 amps. With a 1 amp minimum your LED's might not get the flasher to work.
Another thing you might want to check is battery voltage. If it is low that can keep the flasher from working.
I'm using the LF1-S-flat flasher from
www.superbrightleds.com $8.95 Not sure on shipping. I got my bulbs at the same time. I bench tested this flasher and will flash just one LED bulb. It can handle up to 150 watts of light bulbs, regular or LED. It has been working great for several years. The one thing I found is that it don't like being very close to the ignition coils, especially a high output coil. It flashed very funny when next to my Green Monster coil. I just moved it as far away as I could, it now hangs on the front of the battery box.
Leo