Group tracks not showing in project window

Cubase 7.5 full version, running in Windows 8.1 64-bit.

I copied a full subdirectory of a project to a second computer. I can open the project and everything works perfectly, but when I open the “Group Tracks” folder in the project window it will show the tracks, even though in the mix console and in VST connections group tracks are present that work properly in every other way. When I create a group channel track by right-clicking on the “Group Tracks” folder in the project window, I get a message “added tracks of this type are currently not shown.” I cannot figure out how to reverse this and show the group channel tracks. This only appears to apply to group tracks. I have an FX Channels folder and it behaves normally. I tried deleting the group tracks folder, then creating a group track. The group track creates OK, restoring the folder in the process, but clicking on it still does not show its contents even though I can see the new group track in the mix console and in VST connections.

I am a skilled computer tech.

Please help!

typo - the second sentence should read " I can open the project and everything works perfectly, but when I open the “Group Tracks” folder in the project window it will NOT show the tracks, even though in the mix console and in VST connections group tracks are present that work properly in every other way.

Track visibility filter?