Hi Darcy,
Sonos.CreateGroup always works perfectly for me, although I don't use it very often. Are you sure you are providing the correct player names as parameters for the action?
If you are and it's still not working, then please let me know what kind of Sonos players you are using and post a log file. I only have a "Play3" and a "Connect" to test with but I think it should work fine with all normal players ("Play1", "Play5" and "AMP") but I'm not sure about Playbars and Subs.
You can also try Sonos.PartyMode. It works the same way as CreateGroup but you don't need to pass any player names as parameters.