A dead laptop is hard to diagnose but still, you can perform a series of test before you consider a service centre visit.
Check your Battery Health
Disconnect any External Devices Connected To Your Laptop
Remove and re-insert your Laptop RAM if your HP Laptop Won't Turn On.
Hard reset your laptop
Replace CMOS battery
See more( [https://somnio360.com/hp-laptop-wont-turn-on/|What to do If your Laptop refuses to turn on])