Pick A Selection empty

I downloaded and installed the Nimble builder plugin today. This is the only plug-in active. When I add content, in the “select a content type” I see the Pick a Section and Pick a Module. The Pick a section has 4 drop downs, which from the documentation, shows something should be displayed under each. When I click on any of the four (e.g. Sections for an introduction or Sections for services and features) nothing happens, appears, nothing. just the four choices.

Pick a Module works fine. I can drag and drop a module onto the main space with no issues.

Thanks in advance for your help