I bought 2nd monitor and i want him to be connected to my motherboard not to GPU. I got motherboard MSI B350m Mortar, ryzen 7 2700x, and Radeon rx 580 Aorus. My HDMI and DVi doesnt work on motherboard and i have no idea why.
The Ryzen 7 2700x processor does not have integrated graphics. So you can not use the video output ports on the motherboard.
To use the motherboards video output you would need to use an A-series processor (APU).
Also, the motherboard BIOS will shut off the on board video output when you connect a GPU to the PCIe slots.