Ensure the account is active and there are enough funds available.
Ensure the Account SID is correct and is from your Live Credentials.
Make sure that the API Key used to sign the request is correct and associated with the supplied Account SID.
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.