Why my laptop was locked and I can't turn on my computer
MacBook Air, OS X El Capitan (10.11.1), 2013-mid
MacBook Air, OS X El Capitan (10.11.1), 2013-mid
Please read If your Mac won't turn on - Apple Support. Follow all the applicable steps. For example, Step 6 does not apply to a MacBook Air.
... I should open my laptop and re-insert the battery
Do not do that. Not only will it not help, it is likely to result in catastrophic failure.
Why my laptop was locked and I can't turn on my computer