Commerce File Not Issuing License Upon Order Completion - 7.x-1.0

I've found several postings in various places addressing my issue generally (such as https://drupal.org/node/2145795 and https://drupal.org/node/1221580), but none of the specific fixes have worked for me.

My problem is this: I've set up Drupal Commerce on my site, and it works great up to a point. The only problem is that, after the user is directed back to my website after completing their payment through PayPal, the license for the file they bought isn't issued to them (i.e., when they click on the "File" tab within their profile, it says "You do not have any licensed files.").

Since I'm working in PayPal's sandbox mode right now, I went ahead and changed the checkout complete rule to make orders "Completed" after users have successfully paid through, and returned from, PayPal. However, it's still not working. Incidentally, I'm utilizing the Paypal Express Checkout module to handle transactions through PayPal.

I looked in the debug area to see if I could find if the "order has been paid in full" event is firing after the transactions have completed and if commerce_license is responding and activating the license, as one poster suggested doing in one of the issue threads, but I can't seem to find this information at admin/reports. Perhaps this would be a good place to start, if someone can please tell me specifically how to find this debug information? And also how to act upon it?

Here is the environment I'm working in:

Drupal core 7.26
Commerce 7.x-1.8
Commerce File 7.x-1.0
PayPal EC 7.x-1.0-beta1

All I'm trying to do is allow verified users to access a PDF after they've paid for it. I appreciate any help you can give me.