Lync Phone Edition signs out and then signs back in when it is in idle state

To resolve this issue, install one of the following cumulative updates, as appropriate for the telephone that you use:

• May 2015 cumulative update for Microsoft Lync Phone Edition for Aastra 6721ip and Aastra 6725ip telephones
• May 2015 cumulativeupdatefor Microsoft Lync Phone Edition for HP 4110 and HP 4120
• May 2015 cumulative update for Microsoft Lync Phone Edition for PolycomCX500, Polycom CX600 and Polycom CX3000 telephones
• May 2015 cumulative update for Microsoft Lync Phone Edition for Polycom CX700 and LG-Nortel IP Phone 8540

Note After you apply one of the cumulative updates, you must reregister Microsoft Lync Phone Edition for your telephone because Lync Phone Edition is disconnected from the Lync server. Get the cause of the issue in the "More Information" section in this article.