I am facing an issue intermittently when i use CWMS 1.5 based PCN. The host when presses *1 to dial out to bring someone into conference, the PSTN calls fails saying " I am sorry, the number you dialed is invalid" . Surprisingly its intermittent, the call may pass through after 3rd or 4th attempt.
The issue happens only for external PSTN Calls, no issues at all for internal extensions calling. I doubted that it may be a call routing issue and checked and made sure that the Rerouting CSS of the App_SIP_Trunk contain the partition set for the SIP route pattern. I am not sure what specific needs to be checked for this problem cause.
Appreciate your thoughts on the above.