I have used the UWorld2anki addon for both step 1 and step 2 and haven’t had any problems with it. However, I have recently started Uworld step 3 questions and I haven’t had anything that populate in regards to cards. I’ll finish the questions, click the shortcut to anki cards, and it shows 0 cards pop up in the browser.
You should contact the add-on author – by whatever method is requested on the add-on page.