On a Combiner KVM, when a display is connected to the Console port there is no video output

Combiners are preconfigured for 4K display. Probably your maximal display resolution is less than 4K, like HD. Then you need to configure the Combiner to display 2K  by typing the following keyboard shortcut on the relevant channel:

L Ctrl | L CTRL | F11 | D |4

Need some help?