Can't run script from Toolbar Button

I’ve been working on a script for some time now. It works well from the script editor, but when I add a toolbar button (follwoing the steps HERE) it fails with the error below:

Line 17 of the referenced module is an import statement calling a different module, and there doesn’t appear to be any problems there (since it works from the script editor).

Because the modules work fine from the script editor, I’m guessing there’s something about the way the script is being called. For what it’s worth - I’m using the script editor from Tools>Script>Edit… Not the RhinoScript Editor from Tools>RhinoScript>Edit…

I also found THIS thread, but it doesn’t work for me.

Any suggestions?

Let me know if you need more info.