There is a known issue with the DirecTV 4K Genie displaying an error message "Your TV does not support 4K" even when there is a 4K capable TV and AVR connected. This happens when the Genie box is powered on from a sleep state and the connected 4K capable TV and AVR takes longer to turn on. It is due to this that the Genie is not able to detect 4K connected devices.
While Caavo finds a solution for this problem, there is a temporary fix. Please do the following....
1. Ensure that your Genie has 4K enabled. Go to Settings>Display>TV Resolutions and enable 4K resolution.
2. Turn off power saving mode on your Genie. Go to Menu>Settings>Power Saving.... and disable power saving mode.