Incoming call fails when you use Skype for Business Cloud Connector Edition


Consider the following scenario:

  • Your Office 365 user account is configured to use Cloud PBX.
  • You're using Skype for Business on Windows to receive calls, and the voice for calls uses Skype for Business Cloud Connector Edition.
  • People report that they can't call you.
  • Your Skype for Business administrator has confirmed that your account is configured correctly to receive calls.
In this scenario, an incoming call fails and you receive either a fast busy signal or a recording whose content resembles the following:
We’re sorry, we cannot complete your call at this time.


Use one of the following methods, as appropriate for your situation.

Method 1

Configure the external network interface on the Cloud Connector Edge server to use a public DNS server.

Make sure that you modify the Advanced settings on this interface to remove the Register this connection’s addresses in DNS option.

Method 2

Modify the Cloud Connector DNS server to use pinpoint zones, or add the missing public DNS record (or records) for Cloud Connector to the internal DNS zone.


The Cloud Connector Edition Edge Server cannot resolve the sipfederationtls DNS SRV record for the user’s SIP domain (or domains). A Skype for Business Server logging trace on the Edge server shows the following errors:

  • SIP/2.0 504 Server time-out error
  • ms-diagnostics error 1008 “Unable to resolve DNS SRV record"

The Edge server is configured to use the internal Cloud Connector Edition DNS server, and this server has an authoritative zone configured for the SIP domain.

For more information, see the following Microsoft websites:

Still need help? Go to Microsoft Community.

Article ID: 3157353 - Last Review: Dec 29, 2016 - Revision: 1