Lync 2013 EWS not Working for few users – No Conversation or Missed Call
Verify the Autodiscover is working on user desktop on performing Test Email Autoconfiguration test on Right Clicking Outlook – Select – Outlook Connection.
Type the email address and password and verify the test is successful. Then follow the below step
Login to the user’s desktop – Go to Start – Run – type “Regedit”
HKCUfirstname.lastname@example.org/Autodiscovery named “InternalEwsUrl” and “ExternalEwsUrl”.
Delete the Key, and restart Lync2013. (There is will be no impact since it will get created automatically due to autodiscover)
To know more detail on missed call notification working follow the below url