Okay, I thought maybe that was it. The line on the Compose web page "Import IronCAD files and other industry standard and native CAD files." is what made me expect it to work. I think Compose is an amazing tool for free, but you might want to asterisk that statement or add "with optional translator" to avoid confusion, and also make it easier to jump to the translator purchase page. And instead of "invalid license" could it say something like "translator pack required"?
Again, I am thrilled to have Compose available to my customers as an awesome viewer with lots of additional features. The feedback is just to help you reduce questions and possible disappointment from users. In my case it was that I told someone, "sure you can import that stock part model from McMaster-Carr into Compose".
Scott