Replaced factory cluster w aftermarket. Turn signal issues

If you can’t figure out what it is, sometimes you can figure out what it isn’t. Divide and conquer. I usually jump around troubleshooting, looking for the easy fix to start with. If I don’t find it, then I start over and very methodically check things, working from a starting point. Write down results as you go.

I have a fondness for troubleshooting with light bulbs rather than meters. Meters pull so little current to operate, they can lie to you. An old 1157 tail light bulb in a socket with some long wires attached to it works great. Since the 1157 is the same or similar to the ones you are troubleshooting, it pulls similar current which is good to see if the wiring works under load.