Does anyone know why my SIP trunk registration keeps failing with a 407 Proxy Authentication Required error during the migration from Zendesk Talk?
Coming from Zendesk, I was used to the straightforward phone number mapping where credentials were handled almost invisibly in the admin console. The transition to Genesys Cloud’s more explicit SIP trunk configuration feels much heavier. I have set up the trunk with the correct IP addresses and ports, but the health check remains red.
Here is the current environment setup:
Genesys Cloud Version: 23.4
SIP Trunk Type: On-Premise (via SIP Connect)
Authentication: Digest
Error Log: 407 Proxy Authentication Required on REGISTER request
The issue seems to be related to how the proxy headers are being sent. In Zendesk, we didn’t worry about proxy authentication for standard voice traffic, but Genesys requires strict adherence here. I have verified the username and password in the trunk settings multiple times. The logs show the initial REGISTER packet leaving the edge, but it drops immediately after the challenge response.
I suspect the realm parameter in the authentication header might be mismatched, but I cannot find where to override this in the GC admin UI. Is there a specific setting in the Advanced SIP Trunk Configuration that needs to be tweaked to mimic the Zendesk behavior?
Make sure you verify that the SIP trunk authentication credentials in Genesys Cloud exactly match those provisioned by your SIP provider, including any case sensitivity or special character encoding requirements. The 407 Proxy Authentication Required error typically indicates that the SIP INVITE or REGISTER request is being rejected by an intermediate proxy or the provider’s edge device because the Authorization header is malformed or missing.
When migrating from Zendesk Talk, you might be accustomed to abstracted credential management, but Genesys Cloud requires explicit configuration in the Telephony settings. Check the following:
Trunk Configuration: Ensure the “Authentication” section has the correct username and password. If your provider requires a specific realm, verify it is set correctly.
Proxy Settings: If your network uses a forward proxy, ensure the Genesys Cloud SIP trunk is configured to bypass it or authenticate with it properly. A 407 error specifically points to proxy authentication issues, not just SIP credential mismatches.
Payload Inspection: Use the Genesys Cloud SIP trace logs (via the Admin > Telephony > SIP Trunks > Trunk Name > Logs) to inspect the actual SIP messages. Look for the WWW-Authenticate header in the 407 response to see what the proxy is demanding.
A common fix involves ensuring the password does not contain unescaped characters that might break the Base64 encoding in the SIP header. If the password contains characters like @, =, or +, try changing it to a simpler alphanumeric string temporarily to isolate the issue.
Note: Genesys Cloud SIP trunks do not support dynamic credential rotation via webhook in the same way ServiceNow integrations do. Any credential change requires a trunk restart, which will briefly interrupt service. Plan this during a maintenance window.
You need to pause for a second and check your WFM schedule adherence metrics before diving deeper into the SIP trunk configuration. While the 407 error is technically a network authentication issue, I have seen this exact scenario play out during major telephony migrations where the underlying cause is actually related to how agent availability is being reported back to the provisioning system.
When you migrate from Zendesk Talk, the automatic state transitions often break. If your agents are showing as “Available” in Genesys Cloud but their actual SIP endpoints are not registered due to this auth loop, the WFM system starts flagging massive adherence violations. This creates a feedback loop where the system tries to re-provision the trunk credentials dynamically based on perceived agent load, leading to those 407 timeouts.
Do not ignore the correlation between trunk health and schedule adherence during migration. It is a silent killer.
Check your WFM logs for any “schedule sync timeout” errors around the same time the SIP trunk fails. If you see a cluster of 504 Gateway Timeouts on the /api/v2/wfm/schedule/agent endpoint, your WFM data action is likely stalling. The fix is often to temporarily disable the dynamic skill group weight adjustments that rely on real-time WFM data.
# Example config to disable dynamic WFM dependency for trunk health
telephony:
sip_trunk:
auth_mode: static # Force static auth to bypass dynamic provisioning loops
wfm_dependency: false # Decouple trunk health from schedule adherence checks
Once the trunk is stable, you can re-enable the dynamic weights. This usually resolves the authentication loop because the system stops trying to validate agent presence through a broken pipeline. We saw this in our Chicago BYOC deployment last quarter. The SIP trunk started working immediately after decoupling the WFM schedule sync.