Question No signal on monitor if GPU is installed in the 1st PCIe slot ?

Aug 26, 2021
Hello, so i have a problem and idk how to fix it or who's fault it is. So i got a new gpu (Gtx 970) and when I put it in the 1st PCIe slot i get no signal and the VGA LED is turned on but when I put it on the 2nd slot it works fine but it runs only at x4 instead of x16. Can somebody help me ?

PC specs:

CPU: AMD Ryzen 5 2600
Gpu: Nvidia gtx 970 ( Windforce 3x)
Motherboard: MSI b450 pro carbon AC
16 GB ram ( 2x8GB)
PSU: Seasonic SS-620GM. 620W 80+ Bronze

I've tried another older graphic card (Nvidia gt 610) and it worked perfectly. And this is my new pc, but I have had the same issue (tried with HDMI and DP ports). Now I'm wondering if it's because my PSU is not very good. Thank you.

*Note: I haven't touched too much the BIOS and I think my boot option is not on UEFI