There are four common reasons why your Nintendo Switch is not turning on. Charging cords can sometimes not be plugged in correctly and they easily get damaged, with constant use. Check over your cable for any damage and possibly change it to make sure everything is working as it should.
It may seem obvious but check your battery power. An easy way to spot if your battery has died is when the screen takes longer than usual to light up in charging mode.
Unexpected hardware failure and firmware issues can also prevent your Nintendo Switch from turning on. When we download firmware updates, sometimes it can corrupt or fail to install properly. If it's a hardware failure, this is the worst-case scenario, and you will have to get your Nintendo Switch repaired.