The ECU won't let the engine fire up (or run) below about 7.8 volts so prior to trying anything else, select the voltmeter display and you should see just over 12 volts.
Then turn the engine over on the starter and if the voltage drops below about 8 volts you need a new battery.
This can then be confirmed with a jump start or remote power pack.
By the way, they do bump start OK with a push.
