Hello everyone.
I have HP Omen 25, RX 580 and DP cable. For some time it worked fine. But after I plugged HDMI cable (due to some "little experiments") and then return to using DP cable, Freesync option in Radeon Software became inactive like it's not supported. But monitor's options prove that Freesync mode is on. If I return to using HDMI cable Freesync option becomes active again. It's a mystery...
