“The Dean” is a little confused. You said you were an exchange student. Does that mean you were living in a foreign country and attending classes in a foreign language and thus you supplemented this academic program with online classes in English … or was the online program the ONLY academic program you pursued as a freshman? And, if so, how many other classes did you successfully complete and what were they? (With the answers to these questions, I could answer more effectively.)
In any case, the college folks may be mystified by your two (and possibly three) attempts to finish AP Human Geography online. So when it’s time to apply to college, you should use the “Additional Information” section of your applications (or write a separate letter to admission officials) to explain why you had to withdraw twice from the same course. You might have a very logical reason (or two), and the admission folks need to hear it. If you explain your decision, you will look a lot less “flaky” than if you don’t. Given that you are in an IB program—and assuming that the rest of your grades are good (they are, right? 😉 )– this little wrinkle should not have much of a negative impact–or even ANY–on your college outcomes, especially if you successfully complete the full IB diploma.