Can’t quite understand why the BYOC trunk registration returns a 503 Service Unavailable when replicating the simple Zendesk CTI integration pattern. The environment is Genesys Cloud EU1 with a beginner-level admin config, and the Zendesk equivalent worked flawlessly with just a few webhook lines. The error logs show no specific validation failure, just a blanket timeout from the edge. What specific BYOC configuration step am I missing compared to the Zendesk setup?