I contacted you because a week ago I bought a graphics card RX580 GAMING X DE 8GB.
My idea was to mount it in the 1st slot PCI-E x16 of a motherboard MSI 170 M3 together with an RX 480 GAMING X OF 8GB that would go in the 2nd PCI-E X16 with support to do crossfire.
Somehow when you connect the system recognized them but from the AMD crimson program does not appear the option to enable crossfire, from the bios of motherboard does not appear that option, of course the graphics drivers are updated to the latest launched by AMD 17.11.1.
I will leave 4 screenshots about the system information to see if they can help me saying if any update or requirement is missing.
p.d. thanks u and sorry for my english.