Please ensure that the distance between the phone and the device is close enough and there is no strong interference in the surrounding network environment.
Please check if the entered WIFI password is correct.
Please check if the router is enabled with DHCP. Please make sure that DHCP is enabled.
Please check if the router connection door lock reaches the maximum amount of connected devices.
Please check if the router has special security settings enabled.
Please check if the device is in configuration mode