If it was working fine and then suddenly just didn't turn on today.

The PMU or power management unit might just need to be reset.

To try, here are the steps.

Unplug the power cord and disconnect the battery.

Hold down the power button for 30-45 seconds.

Reinstall the battery and power cord and attempt to power on as you normally would.

If it doesn't turn on try again from the beginning a couple of times, just incase.

Good luck!