(iPhone 8, Samsung Galaxy 9, Macbook Pro late 2016)
(iOS 10, Android Oreo, Windows 10,etc.)
My Question or Issue
Hey @Martinp3812, welcome to the CommunityHope you're doing great!Playing on demand is a Premium feature, that's why you only listen to a 30 second preview of it when trying to play it on demand.
Check this Spotify Answer to learn what can you do with the Free tier on mobile.
I'd also recommend updating to iOS 12.4 :)