[SOLVED] No POST when GPU is installed, but GPU works in other units

[g0rechiLd]

System Specs
GPU: Asus Strix Vega 64 (1st hand, warranty until Dec. 2019)
PSU: FSP Hydro GE 650W (1st hand, warranty until Dec. 2019)
MoBo: Asrock Fatal1ty B360 K4 (1st hand, out of warranty)
CPU: Intel i5 8500 (1st hand, out of warranty)
RAM: Corsair Vengeance RGB 8*2 (2nd hand, out of warranty)

• Unit suddenly hanged and needed to restart, but after that, it won't POST (no keyboard LEDs, but fan, mouse and mobo LEDs light up)
• No beeps when GPU is installed and is not POSTing
• Beeps when no GPU installed and no RAM
• Unit works with on-board graphics
• After a few months, tried to install GPU; it went to desktop, but hanged again and it won't POST (again no keyboard LEDs, but fan, mouse and mobo LEDs light up)

Troubleshooting that I took:

• updated mobo BIOS
• changed CPU thermalpaste
• Reset CMOS
• changed CMOS battery
• memory dance
• BIOS set to PCIE as main graphics adapter
• tried in another PCIE slot in my mobo, doesn't work
• took GPU and went to the seller for repair but it boot and PASSED burn test (using a 650W PSU)
• brought my unit and went to another shop to test mobo; worked using a different GPU (a GTX 1050, I think) using my PSU; my GPU did not work even if it was inserted in a lower end mobo using the same PSU
• tried a Corsair 1000W PSU on my unit, still doesn't POST
• tested GPU on another PC unit, and it WORKED (using a 520W PSU)
• uninstalled Radeon drivers
• reinstalled OS

I don't know what to do next. I just want to avoid buying unecessary parts. Anybody here have an idea what seems to be the problem?

I appreciate the help!

(P.S. English is not my first language so pardon me if there are grammar lapses. Though I will try to explain things to the best that I can.)

 

[g0rechiLd]

All good now, it looks like my GPU was dead. Had to RMA it.