In this case could you please help us with the modem LED light status and have you tried restarting or resetting modem to check for the 2.4G wifi network?
Try logging to the modem GUI to disable and enable the 2.4G network and also need to check for the WAN IP address of the modem.
Launch a web browser, such as Internet Explorer, Firefox, or Safari. Enter http://192.168.0.1 into the address box, and press the Enter key. The https:// Redirect page will appear.
The Gateway > Connection > Wi-Fi > Networks page will appear.
Click on Edit for 2.4 network then click on enable
You can also try changing wifi name and password and
Save settings
Then try connecting devices to 2.4G network and check for the internet.
on the Status option on the left side menu you can check for the WAN IP address.