Hello,
On the Auth0 documentation page ‘Validate JSON Web Tokens’ (https://auth0.com/docs/secure/tokens/json-web-tokens/validate-json-web-tokens), it would have saved me a few hours of time if the instruction steps in the section ‘Verify RS256-signed tokens’ had been more clear.
The instructed download step of the certificate returns a cert.pem file (BEGIN/END CERTIFICATE). This needs to be turned into a pubkey.pem file (BEGIN/END PUBLIC KEY), before proceeding.
Command: openssl x509 -pubkey -noout -in cert.pem > pubkey.pem