Modern Buddy

Took my 125 Buddy out of winter storage (garage) today and installed the battery, which I'd kept on a tender on and off during winter. Am excited to start the season.
But, no juice is flowing. Nothing. Gas gauge not working, no lights, etc. Silent.
The battery was fully charged on a tender, but I took it to Batteries Plus to have it checked and it tested good.

I have an electrical problem somewhere. I shined the battery posts with sandpaper.. In the past this has really been an issue for me to the point where I carry sandpaper. Occasionally the scoot would suddenly not start until I shined the battery posts.
I also checked the fuse and it is good. Again, in the past, I had an episode where it kept burning out. I messed about with different connections, here and there, and suddenly, voila, it worked.
Where do I begin to trouble shoot this? How would you proceed?

Garage kept...hopefully you didn't get mice in the body panels, they love to chew the insulation off wires. Take the nose plastic off and inspect the harness where it leads up to the ignition switch, and shine a light underneath to see if there are any signs of critter intrustion

Stanza: No mice. Our cat sleeps in the garage at night. I may need to remove the panel and check out the connections anyway. It's an idea.