Dell Optiplex 3020 does not work with a KVM switch

I just purchased the Dell Optiplex 3020. I was able to power it on and it booted up fine.

When I connected to my KVM switch (Trendnet 4 port), there is no display.

I swapped the KVM cable with one thats working on another computer and I have the same problem. So that confirms that the cable, port and pins are fine.  If I hit the NumsLock and CapsLock keys they appear to be fine, so I believe its just the display.

Looks like this an ongoing problem with other optiplex devices too https://community.spiceworks.com/topic/329164-kvm-not-working-on-dell-devices.

Is there any workaround? Maybe some setting in the Bios?

Any help would be really appreciated.