I'm not sure if this is a problem with how the phones have gotten provisioned or some other setting we are missing however we have every phone in our office giving the same response in the logs: 8-Jan-2014 16:13:19.844 Leg L:27.3[Extn] is terminated: Cause: 486 Busy Here/INVITE from ..... 08-Jan-2014 16:13:19.844 L:27.1[Line:89999<<...] failed to reach Extn:2025, reason Busy On the phone side of things, the phone does happen to ring but only once and its more of a half-ring that lasts less than a second. And if that failed, this happens: 08-Jan-2014 16:13:27.658 L:28.1[Extn] failed to reach Line:89999>>1723420300, reason Server Failure 08-Jan-2014 16:13:27.658 Call to T:Line:89999>>1723420300@[Dev:sip:9999999999@xxxx:5060] from L:28.1[Extn] failed, cause: Cause: 503 Service Unavailable/INVITE from xxxxx:5060 08-Jan-2014 16:13:27.658 [CM503003]: Call(C:28): Call to <sip:999999@xxxxx:5060> has failed; Cause: 503 Service Unavailable/INVITE from xxxxxx:5060 Phones do not have DND set. We have upgraded the firmware to the latest version of 7.5.5 on the phones as well as up to date on the PBX v12 SP3 as well as the provisioning rules. We have restarted all services several times and outgoing calls are not a problem. Does anyone know what the cause of this may be?