Hello, and Welcome to the HP Support Community!
Is it taking a charge? (Do you get a light when the charger is plugged in?) If not, you may need a new charger.
My ancient ChromeBook misbehaves like this on occasion, I just hold the power button for approx. 30 seconds and it eventually wakes up!
Here's a YouTube video that might help: How to fix a Chromebook that won't turn on.
WyreNut
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Former Expert in the PalmOS, WebOS, and Android sections of this Community Forum.
I am a Volunteer here, not employed by HP.