If you can't associate a published D2L rubric with a discussion topic, it is likely due to an issue with the rubric’s properties. The setting “Allow new associations in Competencies” must be selected for a rubric to be available for associations with D2L tools. 

These directions will guide you through how to update the rubric’s properties to include this required setting:

1. Navigate to Edit Course.
2. Select Course Administration. 
3. Select Rubrics.
4. Select the rubric.
5. Scroll down to the "Options" menu and open it.
   
6. Scroll to the "Advanced Availability" settings.
7. Select the checkbox next to "Competencies."
   
8. Select Close.

Now you should be able to associate the rubric with a discussion topic.