I'm using AMD Radeon R7 200 2GB and just purchased LG 27UD68P monitor, accordingly to LG, my monitor should works on 60Hz with 3840x2160.
Unfortunately, 30Hz is the max that I can choose from the list.
Any advice what would be the problem?
Are you using DisplayPort? The R5/7/9 200 series does not have HDMI 2.0.