The request hash that is declared in the JWT does not match the given request's hash calculated by Twilio. This is a Public Key Client Validation Error.
Possible Solution:
Make sure you are using the latest Twilio helper library. If not using the library, make sure the request hash is calculated on the canonicalized HTTP request and the same canonicalization is used.
For the details on JWTs used as part of Public Key Client Validation, see the documentation