Why the screen off?

@estojerobr31355 check to make sure that this is not a display issue. Darken the room and turn your computer on. Next, use a flashlight and shine the beam at an angle against the screen. If you can make out shadows or shapes you do know, then it is your backlight that has failed. If not then plug the laptop into an external monitor or TV using an HDMI cable. If you get an image on the external display, your motherboard is passing POST but your LCD panel or video cable have failed.

If none of that works then it is possible that your laptop is failing the Power-On Self-Test (POST). This is usually a RAM failure, a corrupted BIOS, or a dead CPU/GPU. Try this. Disconnect the AC adapter, remove the bottom cover, and unplug the battery. Press and hold the power button for 30 solid seconds to drain all residual flea power and reset the hardware logic. Then reconnect the battery and try it.

If that did not work either check the RAM sticks. Remove those and clean the contacts with some isopropyl alcohol. You can also use a pencil eraser for that but do not rub to hard so as to damage the contacts. Next insert a single stick firmly into the primary slot and try to turn your computer on. Test each piece of RAM separately in both slots to find out which piece of RAM is causing the problem. If a piece of RAM does not work in either slot, then that piece of RAM is no longer working. If you use known good pieces of RAM and they do not work in a particular slot, then there is the possiblity of a fractured solder joint on the motherboard. Now if both, clearing the power and isolating the RAM does not bring it back to life, your motherboard may have a component failure which will require the schematic etc. to work on that.

If clearing the flea power and the RAM checked out but its still not working, it could be that the motherboards BIOS firmware is corrupted. Try a blind BIOS recovery. Download the latest BIOS for your exact A15 model from Asus, extract it to a FAT32 formatted USB flash drive and plug it in. Hold Ctrl + R (or Ctrl + Home) while turning on the system to force it to read the recovery file.

To work on your computer use the ASUS TUF Gaming A15 (FA507R) Service Guide which should work for your computer as well even so it is a slightly different model than the one you've selected. It may look different on the inside but essential it's still the same.