SIP Trunk Registration 403 via Terraform GC Provider v1.68.4

Anyone know why the GC provider v1.68.4 returns a 403 Forbidden when applying SIP trunk configurations in AU-1 BYOC? The genesyscloud_sip_trunk resource fails with Error: PUT /api/v2/telephony/sip/sites/trunks/... 403 Forbidden. The payload validates fine via Postman. Using standard OIDC service account. Terraform state is clean.

{
 "name": "prod-sip-01",
 "host": "sip.vendor.com",
 "username": "svc_gc",
 "password": "enc_..."
}