The parallax effect works on lollipop 5.0.2 but after upgrade to 5.1.1 it was gone and not working anymore. Since a few days there is a new update in 5.1.1 again with a bug fix. The problem has been solved. You receive an update message soon, it depends on your country when you get this. Otherwise you can try to download in your google store the app called "parallax 3D background". It only costs 1,16€ and it works. Hope this will help a bit.
Regards
David
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