Question No display after installing new GPU

[sweetsalt]

My friend sold his old AMD 570(8GB) card and got a 1070. He didn't uninstall his AMD graphics drivers before removing the GPU.
His processor is 3600 so with no igpu.
But after installing the 1070 there is no display in the monitor at all. But the system seems to be running as all fans in gpu and cpu are working perfectly fine without rebooting.
What can be the possible causes, he is not that much tech savvy so possible experiences will help me figure out it over the phone.(he lives far)
note: 1070 was mine and it was fine yesterday, I upgraded that's why I gave it to him.

 

[Koekieezz]

My friend sold his old AMD 570(8GB) card and got a 1070. He didn't uninstall his AMD graphics drivers before removing the GPU.
His processor is 3600 so with no igpu.
But after installing the 1070 there is no display in the monitor at all. But the system seems to be running as all fans in gpu and cpu are working perfectly fine without rebooting.
What can be the possible causes, he is not that much tech savvy so possible experiences will help me figure out it over the phone.(he lives far)
note: 1070 was mine and it was fine yesterday, I upgraded that's why I gave it to him.

could he run the gpu on 2nd pcie slot? also what is the system specs in detail?