No certificate found for /O=Digital Signature Trust Co./CN=DST Root CA X3

when invoking “https://dev-ul3fh5s5hd0tojau.us.auth0.com/oauth/token” api to generate token, client application unable to find the ssl certificate DST Root CA X3.

from where download auth0 ssl certificate that client application can use while invoking token api?

hope someone can guide to resolve the above issue.