Solved! Dell Latitude 5490 doesn't boot

[Beunhaas13]

My Dell Latitude 5490 doesn't boot up. Screen stays black.
I've tried booting without the battery and without SSD. Same problem. The power on/off button doens't seem to work right either.
Any tips? What should I check next to find out what's broken?

 

[Behrouz Eydi]

At first check your caps lock tab.if it in flashing mode the problem is Ram.
You should open back and check ram health .remove and set again or replace with eachother or check one by one.
Othedrwise if Ram is ok you have to check display in external mode by vga port or hdmi.