Thanks for the link to the article and your summary, Tim - very interesting and useful. I'm glad I read point 11 and it makes total sense. I had a quiz 'Question behaviour' set to 'Interactive with multiple tries' and wasn't sure why the learner didn't get multiple question attempts.
There needs to be a question 'Hint', as you suggest, something like 'Incorrect response, please try again' or else the question doesn't allow multiple tries. This may be a gotcha for some teachers - I think the necessity to include a 'Hint' should be mentioned in the Editing the question page help.
Cheers,
Chad