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What happens exactly when you try to download it?
Got it. The problem you're having isn't with Spotify, it's with Apple. This actually happens quite often where downloading apps will get stuck on "waiting." There are some fixes you can find for it (e.g. http://www.ikream.com/2016/03/fix-apple-iphone-6-apps-stuck-waiting-status-download-install-update-p...)
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