If you have added a new question to your opportunity, but do not see it under the list of available qualifications to add, it may be a question type that is not available to be used as a qualification.

There are two question types that are NOT AVAILABLE to be used as qualifications:
  • File Upload
  • Image Upload
You will need to create a different question that is of a different question type, edit the existing question, or not use it as a qualification for the opportunity. You may also mark the question as required, and that may eliminate the need for it to be used as a qualification. 

The end date of the opportunity may also have an effect on what questions you see.