Exception during Import Powerpoint

I purchased Articulate Storyline 2 and am in the process of using a free trial of Articulate Storyline 3.  I am trying to import a Powerpoint presentation and I received the following message:

Exception during Import Powerpoint:

The given key was not present in the dictionary.

I am getting this in both my purchased version and in the trial version.  I cannot find information on this particular issue.