Courses from Teachable are not appearing

I see the note on the plugin homepage:

However, after saving in the settings page, the teachable courses don’t appear on the product page. When I choose Select A Course dropdown, no courses appear. I deactivated and reactivated the plugin and I get the same thing — no courses. I also erased the API key and saved, then rentered the API and saved. Still, no courses are appearing. I rolled back to the previous version and the courses are appearing now. Could be a plugin conflict but with dozens of other plugins on a busy ecommerce shop with hundreds of orders a day, I needed a fast solution. I can test for plugin conflicts later if you think that’s necessary.

The page I need help with: [log in to see the link]