In the update process the new binary was made available immediately on the store; but none of the new assets like icons, covertart etc were made available. When I look at the submission info in the dashboard it still shows the first version as being the active version in the store; but it is the new version that gets downloaded.
I faced a similiar issue. For some reason I am able to update on S7 however when I tried to update in S6 Edge it does nothing after downloading. The update button still appears. Do you face this as well?
It seem the update to the apk will be available immediately, but the "review" of the app needs to be set to "approved" again for the assets to change. From my experiences.
