Which subject are you trying to study? It sounds like you might be looking at the SAT section. (If I'm wrong please correct me! 😄) Currently, the app doesn't have any of the practice exercises for SAT prep, only the videos. If you're studying something else, I'll check on the app and let you know whether or not exercises are available for it. 

Same problem. In arithmetic section, and all sub-sections within, there are no quizzes or unit tests when in the app. They are only available on the web-based version.

same problem here in my mobile app, when i logged in using my account in khan from 5 years ago, there is no quiz or unit test displayed. but when using a different account, there are quizzes etc.

Both the iOS mobile app on my iPad and the Android mobile app on my Samsung S7 smartphone have practice exercise quizzes within courses that normally have them.The iOS mobile app on my iPad also has the mastery/mission quizzes, but it appears that the Android phone app does not. Neither the iOS on iPad nor the Android app on my smartphone has the unit tests.

I do not have access to the iOS app on an iPhone or the Android app on a tablet. Also, I have never actually used the Android app on my phone for following a course of study, although I've watched a handful of videos that came up in Google search results for certain topics. I am also now looking at it from time to time to do some support here.