MacBook Air will not turn on? Why?

Solution 1:-

Keep the MacBook Air lid little bit/slightly open. Firm grip and shake it.
Then press the start/power button. This will set of the Sudden motion sensor – SMS and solve your problem.

Solution 2:-

Do the SMC reset. Press and hold Shift + Control+ Option+ Power buttons. Release the keys at the same time. Then turn on your Mac.

http://www.iphonetopics.com/macbook-air-wont-turn-on/

What happens when you try?

Startup Issues - Resolve

Startup Issues - Resolve (2)

Startup Issues - Resolve (3)