The following can help you recover the 4KHDMI device if the unit is on the latest firmware:
Reset Network to DHCP on Device
~ press and hold for 20+ secs. - reverts back to DHCP on a selected NIC
Reset Network to DHCP and Device Interface back to ETH (RJ-45)
~ press and hold until the LCD screen goes black. Then wait 30 seconds and then power cycle the unit. - reverts back to DHCP and RJ45