Unable to Import PowerPoint slides into Storyline 3

Hi Leigh!
I had the same issue a while back. I was using Win7. I upgraded to WIN10 and the import issue disappeared.

what version PPT are you using?
What does the error message state?
any animations or smart art in the PPT? (it comes over but sometimes not too pretty - saw that in a Tim Slade article)

Suggestions:
Try a test import by deleting all but 1 or 2 slides from your PPT. See if it still chokes.
Make a brand new couple-slide PPT and see if that comes across.
(just a wild thought) do you have a bunch of free space on your computer or are you pretty maxed out for space?

Here's a link I found in here discussing what features do port over:
https://articulate.com/support/article/Storyline-360-Tips-for-Importing-Microsoft-PowerPoint-and-Articulate-Presenter-Content

Here's another link in the forum that talks about what to do if your import does not happen:
https://articulate.com/support/article/Articulate-Storyline-360-Failed-to-Import-PowerPoint-Presentation

others (including Articulate staff) will be jumping in here with thoughts.

hope that helps a little
dave