When looking at your Star Coins balance in the Star Stable Friends app, please keep in mind that your balance will not update if you haven’t logged in to the game after receiving an amount of Star Coins. That is simply because the data server has to sync, and if you don’t log in to Star Stable Online after receiving your weekly allowance, for example, the app will still show the old balance.
So don’t panic if you can’t see newly purchased Star Coins or your weekly amount right away if you haven’t played for a while!