The Polycom VVX series "call hold," "transfer," and "resume" features may fail after you install the July 2019 Cumulative Update for Skype for Business Server 2015.


Consider the following scenario:

  • You install the July 2019 Cumulative Update for Skype for Business Server 2015.

  • A user receives an inbound call from PSTN that is answered by a Polycom VVX device.

  • The VVX user tries to place the PSTN call on hold or transfer the call to a Skype for Business user.

  • The hold or transfer fails.  Additionally, if the call is resumed, one-way audio is experienced.

  • SipStack component tracing on the Front End shows the VVX device is receiving a SIP response with the following SIP headers:

    • Start-Line: SIP/2.0 400 Malformed route header

    • ms-diagnostics: 2;reason="See response code and reason phrase";HRESULT="0xC3E93C2E(SIPPROXY_E_ROUTE_SIGNATURE_INVALID)";source=""


This issue is currently under investigation.  This article will be updated when additional information is available.


To fix this issue, install the August 2019 cumulative update 6.0.9319.562 for Skype for Business Server 2015, Front End Server and Edge Server.​

Third-party information disclaimer​

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.

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