To fix this issue, install the July 2018 cumulative update 5.0.8308.1001 for Lync Server 2013, Web Components Server.
UCWA encounters an unhandled exception "System.ArgumentNullException" in Lync Server 2013
Applies To
Lync Server 2013
To fix this issue, install the July 2018 cumulative update 5.0.8308.1001 for Lync Server 2013, Web Components Server.