I regret to say the nightly reward is apparently broken on Android. I went in there yesterday on all characters and came back today, waited past the time shown - no change. I then checked on Chrome and got a "Activate Nightly Reward" screen that I had never gotten on Android. When I click it I get a "come back at" time that is the GMT equivalent of the time I clicked it.

This suggests to me that there is an Android bug (or perhaps just on Samsung Galaxy 10.1 tablet?) where the nightly reward timer won't start and you'll never get a nightly reward unless you go start it in Chrome. Also seems I lost a full day of progress toward the 5th day reward. I'll mail STS but I wonder if others have the same experience?