RC Pro Connection to Screen

I am trying to connect an RC Pro controller to a screen via the HDMI ports via a cable with no luck. When I go into Settings - Display - HDMI there are no Options displayed.
All firmware / Software is up to date and I have used Mr Google with no real results. Any suggestions would be grateful.
It should be noted that this is not a Litchi problem but this forum does get a lot of readers that may have had similar problems.

Here is a similar thread from the MavicPilots forum:

No Luck using the HDMI connection, however I have downloaded ApowerMirror App onto RC Pro, IPad and PC and all works fine via WiFi

Further to my previous I am having difficulty with the mirror from RC Pro in that the Ipad does nor mirror the full screen view from the Controller, hope someone might be able to offer a setting I may have missed.