Excel macro does not show up in Macro list

I made a macro, works fine, shows up in the macro drop-down list.
I saved that workbook as an add-in.
Now, opening a new workbook, Alt-F11 and I can see the add-in, and my code is right there in the module where it should be.
But - when I click on the Macros drop-down, it's empty.
If I manually type the name of my macro in to the macro list box, it runs.
Why does it not show up?
It is not private, it starts like this:

Sub CombineDuplicates()
...
End Sub

Thanks in advance -
Dan