If you have a samsung note 5 the only way I could get back was to make S Launcher the default. Am not sure what helped but here is what I did. 1. Wiped system cache by powering down. Hold volume down, home and then press power. Hold till you see note 5 screen. Then release only power button. 2. Wipe cache. Reboot. 3. Goto apps. Long press on launcher. More info. Uninstall or clear defaults. 4. Press home button. This allowed me to choose launcher. I chose S launcher and ultra power savings mode setting became available to turn off.