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A few weeks ago I've installed OpenVPN for Android from FDroid. Somehow it started to malfunction so I've rebuild the OpenVPN profile. While trying to activate the profile the device showed a screen about that the app should not be trusted and a weird claim that trusting it could result in data being encrypted by the app. I selected the checkbox to permanently trust the app. Unfortunately there was something wrong so I deleted the profile again to start from scratch. The warning appeared again but now I could not select the checkbox and the OK button was greyed out. I decided to delete the app completely and reinstall it. Now I can download the app but clicking on the install button does nothing. It looks like Android has permanently blocked the app or something. The same app downloaded from Google Play can be installed but this one too refuses to activate the profile. What is wrong with Android? BTW: it's Android 4.4.