Error - 20103

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.

First things to check:

• Make sure the Account is active and there are enough funds available.
• Make sure that the API key used to sign the request is not suspended.

To check whether the Access Token is structurally correct, you can use the tools available at jwt.io.

For the details of Twilio's specific Access Token implementation and the requirements of the issuer and subject fields, see the documentation.