Toro z5000 - Just clicks once when starting

I have a Toro z5000 0 turn, pretty reliable, used this season multiple times. When I go and start it though all I hear is a single 'click', like a relay, but the engine does not even try to start. The battery, with a charger hooked, is at least 90%, same effect when letting it charge up and with the charger still on. When you engage/disengage the mower, move the 0turn arms you can hear a quiet click, I expect the safety engaging/disengaging. I do not hear the same from depressing the seat button, but do not think it is that; if I have an arm engaged it does not even make the click sound. Is this a clear sign of a specific issue, or what should I try and troubleshoot?

Toro z5000 - Just clicks once when starting