Hi All, 
R9 390 in general does not have a problem with support for CAC-1070. Perhaps your particular card. Since it is working correctly for the rest, please check with Gigabyte for a Bios update.
Also be sure to remove all Intel Graphics software (if that is on your system).
Please also check for Bios Update for your mainboard, and check in Bios for CSM (Compatibility Support Module). If your Mainboard has such a setting, please Disable that.
Also Disable GPU Scaling in the Graphcis driver in case that is enabled.