After upgrading to Android Lollipop, I am unable to pick calls though the phone plays the ringtone for incoming calls and shows the call as 'missed' later. It does show anything on screen by which I can pick the call. Kindly help. Thanks.
The first thing to check is in
Settings > Sound & notification > Interruptions
that Calls is switched on to allow dialer to bring up the notification window... Then you should get the popup to answer the phone. Good luck though - if your phone is like mine (a Motorola G 2nd gen) depending on what your doing on the phone at the time of the call the stupid call/reject slider doesn't work... WTF - Phones that can't answer phone calls - FAIL!
Under Settings > Sim cards > Check your Connection priority. There is an option to set to "Voice" or "Data".
You must select "Voice".