Do you have the service manual? There’s one here for it but will take you awhile to get to the schematic.
I would check the battery connections and clean them. Think you already did that.
Then check the left hand kill switch assy; starter button, lights. maybe you got rain in the housing—pull off the backshell and spray the connections with contact cleaner—use flux brush to remove any debris. Follow the harness down to the connectors and clean them too. Use a little permatex dielectric grease on a clean flux brush.