I can’t go on Minecraft even though I bought the app

I tried getting on the Minecraft pocket edition app on my iPad Air and it said the I need to buy the app so I went to the Amazon App Store it said that I already bought it a while back but when I clicked on Open to go into the app it said that I couldn’t go on because I “didn’t own the app” so I tried giving a review but that didn’t work either... I don’t know if this is a problem with the app or if it is a problem with my iPad, but I don’t know what is going on with it...