Problem with start Latitude 5289

Hello everyone, 

I have a Latitude 5289 that is showing problems when starting. Basically, when I press the start button, the light goes on including the backlight of the keyboard but everything shuts off quickly. After pressing many times, eventually, it will start.

Things I have done:

I changed the start board, removed the battery, pressed the start button for 20 seconds, run the diagnosis test by pressing F12.

The company that I bought the "Dell Latitude 5289 / 7390 / 7389 2-in-1 Power Button / Volume Buttons Circuit Board with Cable - V30TJ" mentioned that could be the motherboard but I would have to ship it for diagnosis. 

Any suggestions as to next step?

Thanks in advance,

Marcos Albuquerque