Ubercart Userpoints Discounts - can't get the discounts to function. What am I missing???

I inherited a project that had been half-completed and abandoned by another developer. The site involves both an Ubercart and Userpoints installation. The two had never been integrated together until I added Ubercart Userpoints. The site owner wants users to rack up points for interacting with their online community, and then spend the points in the Ubercart store for merchandise or event registration.

When a user has points available, they are able to select Points as a payment option. However, they are not able to select points to apply to a discount on their purchase and then use a credit card to make up the difference. If they attempt to use their points they get an error message that they do not have enough points to make a purchase. No discount option.

Drupal core 6.26
Ubercart 6.x-2.9
Userpoints 6.x-1.0 beta1
Ubercart-Userpoints 6.x-2.0 beta2

All modules (including Conditional actions, etc) are installed, activated and permissions set.
The rest of the Ubercart store is functioning as designed, including credit card processing, typical cart add/remove items, SSL, Signup integration, etc.

Permissions are listed for some of the Userpoints modules (reset, retroactive, pageviews) but not for discount.

What am I missing? I've been able to troubleshoot every last issue in what was a half-baked site except for this one.

Thank you in advance for reading.