Bike doesn't turn on / no lights

[His Dudeness]

I think the mostly likely cause was the connection became loose, which caused increased resistance, which caused increased heat, which melted the connector and started to melt the wire. That continued to happen and got worse over time until the point where there was too much resistance and not enough current could get through to turn on the bike. That would be my guess on what happened. The best fix would be to cut back the wire on both sides of the bad connector until you get to clean undamaged wire and then solder and heat shrink in a new wire and crimp on a new oem style connector.