Motherboard does not detect gpu

[lightgreen]

Hello.
I've recently changed my motherboard, CPU, RAM and PSU ( specs below ) and my graphic card stopped working. Fans are spinning, system boots and... It doesn't detect gpu. According to my motherboard there is nothing in my pcie slot.
I've seen a lot of similar threads, most of them are not resolved. None of solutions I've found worked.
Specs:
GPU: zoltac GTX 970.
CPU: i7 6700k.
Motherboard: MSI Z170 mortar.
RAM: 2x8GB 2133mhz DDR4.
System: windows 10 64 bit.
PSU: Be Quiet! Pure power L8, 700W.
NOTE: before I changed my PSU system was not working because old one wasn't good enough. I've used computer only on iGPU for 4 days.

 

[cin19]

Clear the CMOS. Make sure the pcie cables plug in.
Then try
1) reseat the GPU
2) test the GPU in other PC, make sure it works or not.
3) double check the BIOS setting for the graphic section, make sure it is in auto something like that.
4) try other GPU in your MB to make sure the pcie slot works.