On both my nexus 9 and my Oneplus One running android 5.0.1 the apk installer will pop up and show the permissions but it simply won't let me click install. It does it for apks from the internet and from the Amazon app store. The only thing that I have found is that lollipop doesn't let secondary users install apps but I don't even have secondary users on either of my devices. I searched the settings and haven't found anything, and before you assume that I am a complete fool the "unknown sources" box is checked. How can I fix this?

  • Are you by chance using a screen filter app? – eldarerathis Feb 13 '15 at 1:52
  • I am using a screen filtering app called twilight. I disabled it and now I can install apps again. Thanks! Can you tell me how that works by any chance? – anthony Feb 13 '15 at 1:56
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    It's kind of a security precaution, as I understand it. The theory is that an overlay could try to make you install something malicious or unintended by overlaying a fake app information screen on top of the real one, but letting you tap the real "Install" button. I suppose it could also try to hijack your tap on the button, but I'm not sure. In any case, the system just refuses to process the tap event on the button to try to prevent that from being possible. – eldarerathis Feb 13 '15 at 1:59