Question Vizio P-Series 55" only refreshing at 30 Hz

[airickm3]

I have an entry level 2017 iMac Pro running Mojave 10.14.6 which is connected to
an Apple USB-C to HDMI adapter, which is connected to
an AmazonBasics 15ft Premium HDMI cable (18Gbps) which is connected to
a 2018 Vizio P-Series 55" screen

Despite the fact that each link in that chain supports 4k at 60Hz, when I check the system information on the iMac Pro, it shows that I'm only displaying at 30Hz:

How can I get the full 60 Hz refresh? What am I missing?

 

[hang-the-9]

While the cables themselves may be capable of 60hz at 4k, did you verify the output on the MAC and the input on the TV can run it? On some TVs only specific ports can run 4k at 60hz, check for that also.

 

[airickm3]

The iMac Pro is capable of outputting 4k at 60Hz from the USB-C ports (which is where I’m plugged in) and yes this particular port on the Vizio can take 4k 60 Hz.
I just found the solution the other day - Mac OS Display settings don’t actually show all possible resolutions, but I downloaded EasyRes and then was able to select 4K 60Hz. So it wasn’t the hardware at all, just a software issue.