PC not booting after removing GPU

[RedThunder]

Hi, so i recently upgraded my PC from :

Asus h610-m lx3; Core i5 3470; 16 GB DDR3 10600, GTX 1050 Ti 4 GB, i replaced the motherboard, CPU and RAM and the old part i bought a new case and installed it there to be used for browsing and typing for my kids,

 

the problems starts when i removed the GPU the pc start just fine but no display (note i use an Display port to VGA adaptor because my monitor only has a HDMI and Display port slots), i have tried resetting the bios and removing the motherboard battery but still have the same problem, but if i plugged in my GPU again it boots normally no issue 

 

i have no idea what i should do next, please help

 

Thank you