Not getting back to me regarding specifications I Queried.

Recently I bought a 55 inch 4K smart + LED computer that states its able to run 4K at 60 Hz. But I can not reach these figures through the HDMI slots from my pc. So I Bought a second and a 3rd different HDMI 2.0 cable able to carry 18GBPS. Still only achieved 30Hz. Please can someone from Sinotec get back to me to tell me if the HDMI ports are able to do 4K at 60Hz? And if it can is it available on all 3 HDMI's or only MHL/ARC. Please let me know as at this stage I am really frustrated.