Thanks for stopping by the Apple Support Communities. From your post, I understand that you updated your MacBook, and after it restarted, it would not come back on. I'm happy to help!
The first thing I would suggest, if you have not already, is to press and hold the power button for 10 seconds, let go, then press it once to power it on.
If it still will not come on, the next step to try is a reset of the computer's SMC. You can get more information on the SMC, including what it is and does, and how to reset it, here: How to reset the System Management Controller (SMC) on your Mac - Apple Support .
Have a great day!