The displays can only display what is sent to them. Check the output by using the GAZ emulator.
http://www.phoenix-sports.com/soft_alge.htmThis product will allow you to use any PC as a simulation of the GAZ displays. Makes a simple announcer screen as well.
Just use a serial null modem cable between the transmitting PC and the receiving PC.
If you see the same situation on the emulator the data is not there.