I believe Tourbillon has the key. To clear the cache and maybe the data for your Galaxy Store app navigate to Settings>Apps>Galaxy Store>Force stop>Storage>Clear Cache/Clear Data. Clearing the cache won't cause you to lose any data, clearing the data will affect any settings you've changed from their default value but again you won't lose any data. Everything with your Samsung account is saved or backed up to your account in Samsung's cloud so don't be afraid to try either or both in the pursuit of this issue.
Let us know what you find.
