Game says I don't have a license

I am playing Minecraft Pocket Edition on my Samsung Galaxy S4 and everytime I load up the game it says "You do not have a license to play Minecraft" even though I have purchased and opened it on the Google Play Store. I am very annoyed at this issue as my son would love to be able to play minecraft on my phone when out and about. Please resolve this issue ASAP. as I am very angry and will not be recommending this game to anyone otherwise.