There's no reason why that display should not be working. Optrex DMC series displays have been around for decades. I have an Optrex data book dated October 1990 that lists your display.
Since your other displays work properly and since you can display something on this display then your software and basic setup are most likely correct.
You should start by looking at something that is different with this display and to me what comes to mind are the connections at the LCD.
Don