For people who still have problems with this, here's how to resolve this: 1 - Make sure the TestFlight app is already on your "purchased" list. If not, try to "purchase" the app using your Mac's AppStore, then it will appear on your purchased list. 2 - Delete your current TestFlight app if it refuses to run and keep redirecting you to AppStore. If you don't uninstall your current TestFlight app, download from AppStore will be stuck in confirmation popups. 3 - Now go to your purchase list, find the TestFlight app, and download from there. If there's any popup about downloading an earlier version, accept it. Your download will start. Immediately. Without fail. Probably. (if your previous version is still not deleted, the AppStore will keep showing you this popup instead starting the download process).