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Skype for business can start calls (Video & Voice), but cannot connect. RRS feed

  • Question

  • Hey there,

    A couple of users have a really weird and annoying problem with Skype for Business.
    They can call people (internal S4B users, external S4B users, Skype users and internal/external phone numbers), but when the person they are calling answers, Skype for Business just says Connecting Call for about 10 seconds and then drops the call.

    The exact same thing happens when someone calls them.

    When the chat window opens there is a message saying that the call was dropped due to a network.
    The same error occurred when trying a different network error.

    Any help will be much appreciated!

    Monday, July 15, 2019 4:48 AM

All replies

  • Hey there,

    A couple of users have a really weird and annoying problem with Skype for Business.
    They can call people (internal S4B users, external S4B users, Skype users and internal/external phone numbers), but when the person they are calling answers, Skype for Business just says Connecting Call for about 10 seconds and then drops the call.
    The exact same thing happens when someone calls them.

    When the chat window opens there is a message saying that the call was dropped due to a network.
    The same error occurred when trying a different network error.

    Any help will be much appreciated!

    Monday, July 15, 2019 4:50 AM
  • Hi Tin,

    Did it only happen on specific user machines?

    It sounds like a firewall configuration issue. I suggest that first check UDP 3478 and TCP 443 are allowed in the firewall.

    Then check if it is related to any third-party application.

    In addition, you could collect the client logs “Lync-UccApi-0.UccApilog” under “%userprofile%\AppData\Local\Microsoft\Office\1x.0\Lync\Tracing”  folder. Open it with “notepad”, check any related errors.


    Best Regards,
    Shaw Lu


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.


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    Tuesday, July 16, 2019 1:42 AM
    Moderator
  • Hi Lu

    Yes it happen on specific user use VPN, when we use LAN it ok

    Why i must open port when I use VPN ?

    I will checkin Log in Tracing

    Thanks Lu.

    Monday, July 22, 2019 7:08 AM
  • Hi,

    Do you use split tunnel?

    According your description, it seems related to VPN configuration.


    Best Regards,
    Shaw Lu


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Tuesday, July 23, 2019 9:41 AM
    Moderator
  • Hi,

    Is there any update on this case?

    Please feel free to drop us a note if there is any update.

    Have a nice day!


    Best Regards,
    Shaw Lu


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Friday, July 26, 2019 7:56 AM
    Moderator