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Unable to set private mode, store WiFi passwords and install Knox on Samsung Galaxy S7


New member
Jun 7, 2016
Hello all, I am fairly new to Android so forgive my lack of knowledge. I tried searching for my issues for a few hours on this site and many others, and I'm not quite sure what's going on. Basically, I bought a used Galaxy S7 with 6.0.1 installed, which is in great shape, but for a couple minor issues. Here they are, in no particular order:

  • When turning on private mode and inserting my security pattern, it says "Failed to turn on Private Mode. Try again"
  • I constantly receive a "Security Notice - Unauthorized Actions have been detected. Restart your device to undo any unauthorized changes" (restart doesn't change anything)
  • Phone won't remember WiFi settings and password, I have to continually type in WiFi password when connecting
  • When trying to install My Knox, I get the following warning "My KNOX cannot be installed because a custom OS has previously been installed on this device."

I have a feeling that the previous owner had rooted the phone, and messed around with some root files before selling it and resetting it back to factory settings, but that's just my amateur assessment. What are some steps I can take to remedy these problems, and any future problems? Thanks for your time, guys! Sorry if I broke protocol or anything!