I have a 2018 Nissan 370Z, recently pulled the engine and trans out (together) to install some twin turbos.

I finally have everything back in and connected - but it won’t crank.

I suspect it’s the battery, as I left it without a trickle charger for 6 months, however, the multimeter says it’s above 11.8V with no charger support.

The starter motor makes a loud “click” but doesn’t spin the flywheel.

I can manually turn the crank pulley with a driver to ensure that the pistons can move properly, was a little paranoid re: fuel as I’ve upgraded the fuelling system.

Alternator is plugged in too.

Unsure why it won’t start. I have checked the connections and they’re all tight, high beams and low beams work fine too.