Hi @Phong Vu , I can see permission issue in Sandbox account.
I am calling 2 events in my subsciption
"/restapi/v1.0/account/~/telephony/sessions?direction=Inbound&missedCall=true",
"/restapi/v1.0/account/~/extension/~/voicemail"
I have created subscription multiple times. and called subscribe, get and delete a subscription multiple times but no luck.
My client id is ZfgY0sK_SlG1eubfv0zr7g
Are you able to see if I am missing anything?