2013 T800 turn signal problems

I noticed tonight that the unit has no rear signal light on the headache rack or the trailer on the driver side but my signal on the rear skirt works. My marker lights on head ache rack all work as do my brake lights and four way flashers along with the signal lights on the passanger side i replaced the lights with new one and still no signal any ideas where to start checking thanks in advanced p.s im new at this