Question PC wont Boot Up after installing a new graphic card. (RX 470 powercolor)

Mar 8, 2019
Destop Spec.
PSU 680Watt
MB: H81M-VG4 R2.0 (V 1.5 UPDATED)
GPU : RX 470 Red Devil Powercolor 4GB

I recently upgrade my GPU from GTX 650 1GB (6PINs) to RX 470 4GB (8 PINs). Both the 6Pin to 8pin converter needed to power it up. However when I tried to turn on the computer it does not boot up. When I detached the GPU it boots up normally. I've tried to look for solution for several days and found a few possible solution but to no avail.
  1. Uninstall the previous GPU program (Didn't work)
  2. Update Bios (Updated my bios from 1.2 to 1.5 but still didn't work)
  3. Change the monitor cable (IDK if this had something to do with it, but I changed it anyway and nope, still not working.

I wonder if its the 6pin to 8pin converter that has got problem.

I've looked at the previous posting, digs out the old thread but most of them are unsolved / the solution does not works for me.

Thank you!