I'm trying out the free version to see how it will work with my first attempt at using Google Classroom. After doing the import, I see that it hadn't imported all of the assignments and on the ones that were imported were not in the correct deadline order. Am I misconfiguring something?

Here is what was imported into the Gradebook.

It looks like you are using the limited version (which imports a maximum of 5 assignments), you can get a free 15 day license here to test out all of the features:
https://www.gdevapps.com/free-trial
To purchase:
https://www.gdevapps.com/product-page/gradebook-for-google-sheets-and-classroom