I have the same issue.
A course allows guest access to 2 presentations but if you want to take the SCORM quiz and get a certificate you need to be logged in.
Logged in users can complete the quiz but because they are not enrolled (or prompted to be enrolled), their scores are not recorded and can't get the certificate due to conditional settings.
I have the quiz hidden for guests and a label describing the requirements (logged in etc) but still would like to see them enrolled if viewing the course and logged in.
Any advise?