I couldn't edit my question, so posting a comment.
I have checked Gateway Audit events, I tried with httpbin api, same error,
Problem routing to https://httpbin.org/ip. Error msg: Unable to obtain HTTP response from https://httpbin.org/ip: Certificate not verified. Caused by: Certificate [cn=*.httpbin.org,ou=essentialssl wildcard,ou=domain control validated] path validation and/or revocation checking failed