R9 390 won't work with my cintiq pro 16 at 4k resolution
I can't get my Cintiq pro 16 to work at 4k even though the option in the display resolution says: 3840x2160 (recommended). It only works at 1980. Anything else, it goes to black, no signal and then reverts to 1980. I've tried the same cables on my other pc, which has an nvidia graphics card and it works perfectly at 4k. Same cables and same Wacom drivers.
I've tried different wacom drivers to no avail and different amd drivers also.
Graphics Card: Gigabyte R9 390
CPU: Intel Core i5 6600K @ 3.50GHz
Motherboard: ASUSTeK COMPUTER INC. Z170-P (LGA1151)