The issuer or subject of the Access Token provided to the Twilio API was invalid.
Issuer: The API Key used to sign the the token.
Subject: The Twilio Account SID from your Live Credentials.
To check whether the Access Token is structurally correct, you can use the tools available at jwt.io.
Access Tokens are used by multiple Twilio SDKs, including Programmable Voice, Programmable Video, and Programmable Chat. For the details of Twilio's specific Access Token implementation and the requirements of the issuer and subject fields, see the documentation.