1985 Suzuki GS450L Starting issues

I have a 1985 Suzuki GS450L that ran fine until I let it sit far too long after getting a larger Yamaha XS850. I totally expected to rebuild the carbs as I prepare it for sale. But I found it wouldn't turn over now. I bought a new battery and also a new ignition switch when I saw intermittent power when turning it on. But when pulling in the clutch and pressing the starter button, nothing happens. No clicking or clunking from the solenoid. The fuse is good. If I cross the main solenoid terminals, the engine turns over. I checked for power on the green/yellow wire to the solenoid, and none is present. I ran a jumper straight from the positive battery terminal to the terminal for the green/yellow wire terminal on the solenoid and I get a clunk as the solenoid engages. So obviously there is a breakdown of a power signal to the solenoid. From there I am confused to trace the problem down. Where should I start tracing this from and to each connection point along the way? Thank you for any help here.