Sympton:
Unit  is not stable, blue screen, system not stable, no boot to OS, boot directly to BIOS)
Unit has charger plug-in, but the charging and LED is not on.
When the unit is powered on, power, charging and HDD LEDs are not on.
Unit can pass MRI test and stress test, but it is not stable. It eventually got bluescreen or powered on go right into bios with detecting the HDD.

Even with the HDD I/O baord and USB I/O (where LEDs reside on) replaced. There is no sign of LED on indication.
Memory tested good.

Answer: It is the defected mainboard.
Solution: Order mainboard and replace it.

Example Models:
X555LA-BH51-CB

Many Asus laptop has HDD IO board issue. Unit cannot detect good HDD.
Solution: Just order and replace the HDD IO board. Do not sent the board for repair, because it may happen again.

Example Models:
X555LA-BH51-CB <= IO boad v3.0 or above
X555QA-BB10-CB A10 9600/12G/1T/15.6
X555DA-SS10-CB