Not able to store Wi-Fi network passwords in keychain
Keychain First Aid may solve your problem. It has been removed in later Mac OS versions (starting with 10.11 El Capitan), but it should still be available for 10.10 Yosemite.


Launch the Keychain Access app, located in Applications > Utilities
From the Keychain app, go to the Keychain Access menu in the top-left and then select Keychain First Aid. 
From the Keychain First Aid window, select Repair and click Start