There are two common causes for this error, each listed below. In either case, you will need to access the router setup screen to view the network details or to make changes. Refer to the manual supplied with the router for instructions.
WiFi network password or grill information was entered incorrectly.
Verify that the home WiFi network name and password are correct.
The grill is attempting to connect to a 5GHz home WiFi network rather than a 2.4GHz network.
Many modern routers broadcast on both 5GHz and 2.4GHz bands. Verify that the WiFi network that the grill is attempting to connect to is a 2.4GHz network. Two factors may be causing this confusion: