Retaking diagnostic

How can I retake a diagnostic exam?

I'm doing LSAT prep and halfway through the diagnostic exam I realized that there's no way I can do this without my ADHD meds, so I tried to quit in the middle. Turns out I could only resume the exam, not restart, so I just hit submit on everything with a bunch of answers missing. Now I don't see any place where I could go back and do the diagnostic again. I don't think the prep focus is going to be particularly useful for me seeing as it's based on assuming I don't understand entire sections that I skipped.

Where is the "start over" button?