Thanks for the advice. It worked. A bit confusing after clicking RESTORE when it says the app will be uninstalled, but worked it out. DO NOT uninstall it. And you have to pull down the quick panel, select edit, and drag the icons back to the top level, then click DONE.
Same. From 08:00 when it was working to 10:40 when it wasn't. Bad move by Samsung?
Meanwhile, to turn on/off go to data usage screen. Tethering has also disappeared. Have to go to settings panel now.
Might have to try another launcher.