2015 Prius C: 'Check Engine' light on - nothing else.

2015 Prius C; original owner; 39755 miles. Remote start installed at purchase.
Car not driven for one week due to virus interruptus. Would not start - only light on dash was 'check engine'.
Attached battery charger to jump-points under hood, charger set to 'high / start'.
Turned key - dash lights came on and 'Ready' indicated. Disconnected charger. Engine cycled on for a couple minutes then cycled off.
Backed car from garage; I shut it off for ~5 minutes; car restarted / cycled properly.
I did not check voltage or use a tester on the battery - Yet.

To me, it appeared as if the system went into a 'lockout'?

 

The trim, I believe, is a two and uses the smart-key on the column to start. It does have that red light indicating that it's searching.
I thought perhaps there was some sort of system lockout at play here.
Tomorrow I'll yank the rear seat and unhook & test the battery.
Thanks for the assist.

 

I have not yet tested the battery, plus the problem has not reoccurred (yet).
I agree that the battery is probably on its way out although the intermittent red dash light for the remote combined with the two blue intermittent lights on the remote start antennae (indicating locked doors) may have slowly drained the battery while the car sat for a week.