The HDMI video output ports of the TBT3-UDZ dock support the HDMI 2.0 standard.   

If a monitor supporting HDMI 2.1 is not working or not working at the maximum resolution when connected to the TBT3-UDZ via a HDMI video cable, please consult your monitor's user manual in order to see if the HDMI version setting can be changed to version 2.0 or 1.4.

If the HDMI version can be changed, please change the HDMI version setting to a lower version number and then test the behavior again.