my mac does not turn on after installing macOS catalina

Hi,

If your Mac doesn't turn on.

https://support.apple.com/en-us/HT204267

If it doesn't help, contact Apple Support to tell them the circumstance you face with now.

https://support.apple.com

press the power button down for 10 seconds

then reset pram

was this power failure during the install?

a lot of users have experienced this set back.