I've just bought an RX570 and it won't let me select a resolution higher than 1920 to my 4k TV or 4k AV receiver over HDMI.
It all works perfectly with my old card (a GTX 750) and I am able to run 4k at 60Hz. I am using the same high-speed cables that work fine on my old card (and also work fine with my laptop).
I tried setting a custom resolution, but it says it is not supported by my display (even though it is).
Any ideas would be greatly welcome....