Can’t view quiz questions

Whenever I try to access the questions to a quiz, the following shows up:

Error: ! Please try again.

All the other tabs work – I can change the settings, and the questions appear in the preview. The error just pops up under the “Questions” tab.

In the console, the following error shows up:

Response to preflight request doesn’t pass access control check: No ‘Access-Control-Allow-Origin’ header is present on the requested resource.

Followed by a 404 error. I’ve tried using a few different themes and disabling other plug ins.

Thanks