Thanks for all the suggestions.
I did have the Foster Systems/Exploradome selected under Extra-Dropdown/Observatory/"AstroMC Dome/Roof Driver" and connected. At least, it was indicating that it was connected. Perhaps the Foster System is not communicating out its status. I'll follow up with the Foster Systems guys.
When I do connect to the "AstroMC Dome/Roof Driver" and then select Settings, I get an error box from the Foster System saying "No setting required", so there seems to be some kind of communication between the two.
Maybe someone with a Foster Systems controlled dome will chip in.
In the meantime, will try the SGP Slaving option and report back.
Dave