Mac won’t turn on

Depending on the age of the computer, the amount of use its hardware has

sustained, and the cycles of charge/discharge of battery; these may add up

to show a need for some repair or replacement of expendable parts.

These items may need attention (replacement) as part of troubleshooting:

battery, magsafe (or other kind charger, if newer) and/or 'DC-in Board'. Plus

the hard drive may be worn, damaged, or cause data corruptions.

Troubleshooting the hardware can begin by attempting the few resets one

can attempt to see what (if anything) tries to awaken in your comatose Mac.

Some resets can affect the software at low level; in effect issues that may seem

like hardware may be at least partially due to data corruption or bad hard drive.

If you experience issues with sleep, wake, power, charging your Mac

notebook battery, or other power-related symptoms, you might need

to reset the SMC (System Management Controller). Or NVRAM or PRAM

reset per each instruction detailed page, may help try & see what's up.

To identify the machine, its configuration (build year model and hardware mix)

plus operating system; would be a base-level starting point. ~ If you happen to

have a 'bootable external system clone' on self-powered hard drive, that may be

a good place to see if a restart from an quality copy clone/backup gets it going.

Sorry to not be of much useful advice; there's not enough here to work with.

A whole slew of 'startup troubleshooting measures' can be read about here:

• Mac Basic Startup Troubleshooting Steps - Apple Community

https://discussions.apple.com/docs/DOC-250000361

Helps to relate more info about your computer to narrow probable cause/s.

Try the steps in this Apple article. Just unplugging the power adapter from the electrical outlet for a minute can reset the power adapter. Also try using another electrical outlet.