This solution describes how to change the wifi network on an existing smart home hub.
Please follow the steps:
1. Disconnect the hub from the power (Smart Home Hub must be displayed as offline - so you will need to wait until Smartthings marks your hub as offline/disconnected).
2. Open the App
3. Switch to Devices
4. Tap on your Smart Home hub
5. Click on the 3 dots in the top right corner and then on "information"
6. Click on Update Wifi information
7. Connect the Smart Home Hub and wait until the blue LED turns on
8. Press the reset button until it blinks yellow
9. Scan the QR code
10. Press Connect
11. Select your Wifi and enter the password
12. The change from Wifi is complete.