In this case we would suggest you to change the Wi-Fi security modem before connecting cameras to modem Wi-Fi network.

Login to the modem GUI 

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 Username field has admin populated, enter the custom password in the Password field.

Click the Login button.  The Gateway > Summary page will appear.

Select Gateway > Connection > Wi-Fi > Edit Home 2.4 GHz

Click on the security mode drop down arrow and select  WPAWPA2-PSK(TKIP/AES)

Click on save 

Then restart or power cycle the modem for a minute and try connecting cameras to modem 2.4 network.