Unable to access 2.4GHz on El Capitan

My Macbook Air (Mid 2012) is not able to detect 2.4 GHz signals after upgrading ro El Capitan. Is this something that is common. although it is able to detect and connect to 5GHz, but for 2.4 after yesterday's update it has stopped even showing the SSIDs.

Appriciate help on this. Thanks