Double check the password is entered with the correct capitalization. There is a switch to see the entered password that can be used to verify this.
The industry standard for the majority of WiFi router manufacturers maintain the capability to connect to a 2.4 GHz network directly upon powering up the router. If the router has both 2.4 and 5 GHz capability, then this will be viewable for the majority of routers in the WiFi network (SSID) name. The suffix of the network name should indicate whether it is 2.4 or 5 GHz.
In the event that a 2.4 GHz network is not available from your list of selectable networks, please refer to your router manual or IT specialist for further information.