Rear turn signals dont flash but fronts do.

[BigChevy]

My rear turn signals do not flash on left or right. The front signals flash as they are supposed to. The rear turnsignal running lights are on, so i know there is power to the bulbs. Any ideas what could cause this? i have traced the wires from the switch all the way to the lights and have not been able to find a break in the line anywhere. they all worked when i first got the bike. one day i started her up and they didnt work. any advice is appreciated. thanks.