Answered my own questions. I was returning the XML through the RibbonID
ratehr than as the return result (IRibbonExtensibility_GetCustomUI=[xml])

"Jeff Abbott" wrote:

I am using VB6 to implement AddInDesignerObjects.IDTExtensibility2,
Office.IRibbonExtensibility, and Office.IRibbonControl

My Add-In loads fine; the followign methods are called:
IDTExtensibility2_OnAddInsUpdate
IDTExtensibility2_OnAddInsUpdate
IDTExtensibility2_OnStartupComplete
IRibbonExtensibility_GetCustomUI

And I am able to pass the customUI xml for a document Add-in that I copied
from the article: http://msdn.microsoft.com/en-us/library/aa338202.aspx

I don't see anything that would make the xml specific to a documetn Add-In,
but I don't get any new tab in Excel, or PowerPoint if I switch that through
the designer GUI.