My MacBook is fully charged but not starting ..someone help

Should you have read & tried instructions in companion article on this page

and nothing happened; then consider an appointment with authorized or

official Apple repair. They can check Mac over, & suggest a course of action.

(This assumes AC-adapter connection is good & Mac gets a charge from it.)

If your Mac doesn't turn on

~ in part, from above support site:

"..follow the steps for when your Mac doesn't start up all the way.

If your Mac still doesn't turn on, please contact Apple Support."

~ Or try whatever the difference, between the above article & this one:

• How to Fix a Mac or MacBook That Won't Turn On or Start Up | MacWorld UK

https://www.macworld.co.uk/how-to/wont-turn-on-boot-3423817/