I'm having the same problem on a Verizon S8+. After the Oreo update my navigation bar completely disappeared. I've tried:
1. Swiping up from the bottom of the screen: no change, from home screen or in app.
2. Checked the navigation bar settings (toggled the hide option, it was already off): no option made a difference.
3. Changed themes/launchers - I was using the Material Dark Samsung theme and Nova launcher. I ultimately resorted to stock touchwiz: again, no change. Even after multiple restarts.
4. Started the phone in safe mode: navigation bar was still missing!
5. After several days of no luck, I factory reset the device. It was fixed! And then it wasn't.
At some point while setting up the phone, the nav bar disappeared again. I went through the above steps again, but no luck. I factory reset the phone again and am in the process of setting it back up, paying a little more attention this time.
03-22-2018 04:22 PM