If it is battery issue, remove battery from laptop and try again, but it sounds like a motherboard cmos issue.
Hi everyone, One of our users has a Latitude 7400 2-in-1 that won't power on. Keyboard or power button don't light up. Only on the side the LED indicator lights up with an amber light and stays on if you hold the power button. I tried disconnecting the battery and holding it for 30 seconds and then plugging in an AC adapter but the same thing happens with the indicator.  [IMAGE] Is this a battery or a mainboard issue?  Are there any other tests I can do, to try and fix my issue.
Latitude 7400 2-in-1 Won't Power On. Solid Amber Light When Holding Power 
Button.