Monitors fail when connecting 2 monitors

I’m using 2 ACER G276HL monitors on a Dell Optiplex 3040 computer. 1 monitor is plugged into the UD3900 using the DVI connection. The other monitor is plugged into the computer using an HDMI to DVI cable (monitor has the DVI). Everything else (mouse, network) but the one monitor is plugged into the UD3900.

Everything works fine when connected in this way.

When I move the HDMI cable from the computer to the UD3900, neither monitor works right - I get a background display on both monitors and can see the mouse cursor move, but I don’t see anything else.

When I move the HDMI cable back to the computer, everything works well again.

I have tried uninstall, cleaning, then reinstall of drivers per another topic instruction but I get the same results.

What can I do to get both monitors working via the UD3900?

Hi Ron,

Thanks for the post! When using our docking station with a desktop computer, there has to be a monitor plugged in directly to the computer for it to work. You can still use both ports on the docking station to add a 2nd and 3rd monitor, but you always have to have one monitor hooked up to the desktop.

If you have any other questions, please feel free to contact us directly at

Thank you!

Thank you.