In short, remove power, unplug battery, press and hold the power button for 60 seconds, release, put in battery (unless it's a bad battery), apply power and re-test. How old are these units? Over a few years and I change the CMOS battery.
For reasons I can't guess, some client push back on changing the 25 cent battery. We want to eliminate the cheap things.
Hi u have 2 HP laptops they have both been working perfect and tonight ave put them on to charge and ain't switching back on. Both have light to indicate they charging just ain't switching back on any thing that could help thank you