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SIP Response Codes

This page provides guidance on SIP response codes, their meanings, and potential actions to resolve issues, supporting you in troubleshooting voice agents. You can find these codes in Cognigy.AI Logs of your Agent under sip_status, or in downloaded PCAPs for specific calls. For troubleshooting, check the Alerts page in the Self-Service Portal for any received alerts.

Code Error Description What to Do?
200 OK The call was successfully answered. No specific actions are required.
202 OK The request has been accepted for processing, but the processing has not been completed. No specific actions are required.
400 Permission Denied The server refuses to authorize the request due to various reasons, including the user not having necessary permissions or having wrong credentials. - Check the request credentials (for example, user name and password) and permissions.
- Ensure the request is being sent to the correct server and endpoint.
- If there are a large number of requests with status 403 from the same IP, consider blocking the IP.
404 Not Found A call to a phone number not set up in the Voice Gateway Self-Service Portal may indicate a SIP spam attempt. - Check the Carrier or Phone numbers configurations in the Self-Service-Portal.
- Verify the request URI provided in your Transfer Node is correct. The issue may be due to a mistyped address or an outdated record.
- Investigate further for troubleshooting and possible IP blocking.
408 Request Timeout The SIP endpoint was unresponsive, and the server did not receive a complete request message within the time it was prepared to wait. - This often indicates network issues or a problem with the server. Try sending the request again after some time or investigate network connectivity problems on a lower level.
- Check and compare Voice Gateway PCAP for a specific call with your provider's PCAP for that call.
480 Temporarily Unavailable There is no application configured for an incoming call, or if there are no more resources available to handle a call (the system is at maximum capacity). - Check if an application is properly attached to the Phone number in the Self-Service Portal.
- Retry after some time. If the issue persists, contact the callee by other means to confirm their availability.
487 Request Terminated A call is terminated by the caller before the connection is established. No specific action is needed if the termination was intentional. If unexpected, inspect the call Flow for issues, for example, faulty Code Nodes.
488 Not Acceptable Here The incoming call requested a codec or a feature in the Session Description Protocol (SDP) that the Voice Gateway does not support, or it provided an unacceptable parameter. Check the codecs or any other session parameters being used and ensure they are supported by both the caller and callee.
500 Server Internal Error The application error. The server encountered an unexpected condition that prevented it from fulfilling the request. This is a server-side issue. Attempt the request later or contact the server administrator if the problem persists. For example, if the Voice Gateway responded with this code, contact Customer Support. If your carrier responded with this code, contact your provider.
503 Service Unavailable Voice Gateway is unable to process the call due to specific reasons, including an inactive account status or reaching the maximum call limit. Contact Customer Support or your Customer Success Manager at Cognigy.
603 Decline The callee's end system was contacted successfully but the user explicitly rejected the call, or there was an issue connecting to the Voice Gateway Endpoint. - If it was a normal rejection of a call, no further action can be taken to establish the call. If necessary, try contacting the user through alternative means.
- If this response was not expected, check your Self-Service Portal configurations of your Carrier as well as the Alerts page.
- Check Cognigy AI logs for any error log messages that could indicate the root cause.

If you encounter any difficulties resolving your issue, contact Cognigy technical support.