SIP INVITE 403 Forbidden during JMeter SIP load test

Could someone explain the following behavior during a SIP load test:

  • Using JMeter 5.6 with SIP plugin to send 200 concurrent INVITEs to Genesys Cloud US1.
  • Receiving 403 Forbidden immediately after the first 50 calls succeed.
  • Auth credentials are valid and the user has full permissions.
  • No rate limit headers present in the response.