Diagnosis
The microwave is in pairing mode but cannot connect to your 2.4 GHz Wi-Fi network. It does not support 5 GHz bands.
How to Fix It
Follow the exact sequence. On the microwave, press and hold the WiFi button for 3 seconds until 'AP' appears. On your phone, go to WiFi settings and connect to the network named 'SamsungOven_XXXX'. Then open the SmartThings app to complete setup.
If That Didn't Work
Your router may be blocking the connection. Temporarily disable your mobile data. Disable any VPN on your phone. Ensure your router's firewall doesn't block new device provisioning.
Heads Up
The microwave must be within strong range of your 2.4 GHz router. Physical obstructions like walls and large appliances significantly weaken the signal.