iOS 10 Test Flight Download Failed

I have upgraded my app to work on iOS 10, with xCode 8.

xCode builds the app successfully, and then successfully uploads it to the iTunes Connect. But when I try to install it using test flight, it throws an error, “Unable to Download App”

Has anyone else had this problem?

Also, when I try to install the app using iTunes, it never finishes syncing, and cannot install the app. Seems to be related to the same issue.

Update: I just needed to delete the older version from my phone before downloading the newer version!