My computer will not turn on and I’ve pressed the CTRL, shift, alt, and power button at the same time. It still will not turn on.

Read and follow all the instructions in If your Mac doesn't turn on - Apple Support, all the way through and including the end, which concludes with:

"If your Mac still doesn't turn on, you need help with these instructions, or you don't have the items you need, please contact Apple Support."

Hi,

Following article could help your issue.

If your Mac doesn't turn on - Apple Support

If it doesn't help, you'd better make Genius Bar reservation if your local retail AppleStore is open or find opened local Apple Authorized Service Provider to be examined your MacBook Air there.

Genius Bar Reservation and Apple Support Options - Apple

Apple - Find Locations - Location Selector