Although you most probably saw the email answer you got from [email protected] just to make sure ….
I am quite sure your TV has 2 HDMI2.0 port supporting 4K 60 Hz.
Setups with TV’s normally work best by making a custom resolution, in this case for: 3840*2160 at 60 Hz with Timing Standard set to CVT-RB (Reduced Blanking ).
(For setups with Monitors Timing Standard can remain on “auto”.)
On most TV’s you will need to do some settings like “Enhanced Mode”/ “PC-Mode” and/or “UHD Color” for the HDMI 2.0 port in use.
Please make sure the HDMI port of the Screen/TV supports 4K 60 Hz, often not all HDMI inputs support that.
Please make sure the Software of the TV is updated
Please make sure the HDMI Cable is capable of 4K 60Hz / 18Gbps.
To make a custom resolution on MAC OSx and do that Timing Standard setting, you will probably need to make use of a program like SwitchResX.
Make sure to make use a new users (or first remove all existing users when you already have used SwitchResX before).
We do have user feedback that they have it running without such setting on 10.12.4, this does sometimes involve making new user or even re-installing the OS completely …
Apparently old files are “in the way” when using the upgrade feature …