Replaced factory cluster w aftermarket. Turn signal issues

I don't know much about aftermarket harnesses. Just edumacted guessing. Looking at the pic, Pink appears to be ignition or switched 12 volts to everything.
The tan wire,,, Maybe some applications require a wire back toward the firewall or kick panel where the factory wire from switch is accessible. I'm considering all those with foot operated park brake. The switch would be there. Tan wire would route from the (-) side of LED back that direction on the tan wire. You probably could use that smaller Tan from the (-) side of LED and attach it to the factory black wire somewhere besides right behind your inst' panel.