Im having the same problem. I've had it for 3 days now and no.matter what I do it just goes back to saying "Check ypur phone to complete setup." If any solution was ever found PLEASE let me know I am extremely frustrated.
Hard reset did not helped me at all!
But here is what I did to FIX IT
1. Hard reset on watch
2. Reinstall the gear s app(iTunes)
3. Forget old Bluetooth connection in settings!!!!!!!!!
4. Open the app and it will show you Available Gear Watches to connect to.
Use the Gear S app to set up first connection
(Connecting throug system setting did not worked for me so Do Not Try it)
Just connect through the reinstalled app
5. you may restore some of your setting later when login in to Sams Acc
Have you tried clearing the cache and data on the Gear Manager application? You can do that by going to Settings>Apps>Gear Manager on your phone, then pressing Storage. The options to clear the cache and data are in there.
This worked for me
I have just bought new Galaxy S9 and 46MM silver Bluetooth Galaxy Watch. Will not complete setup. The Wearable App screen showed 1-100% completing setup then stalled there for hours. Phone gets stuck in "Setting up your phone...Almost there." message with Cancel button greyed out with spinning galaxy background. Watch says "Check your phone top complete setup." Watch works with WiFi well when in stand alone mode.
1. Uninstalled and installed Wearable app from both Playstore and Samsung Apps stores.
2. I cleared and deleted the cache and data in the Wearable app - storage.
3. I restarted the watch in regular mode and hard reset watch several times.
4. I restarted the phone in safe mode but the wearable app was greyed out and would not open at all.