Problem

-- When trying to use a Connect to URL filter to connect to an HTTPS backend server, the connection failed and the error:

The certificate was not issued by the domain issuer

appeared in the trace file of the instance.

-- It may happen on some previously working connection.

Resolution

- If configuration is right (certificates chain imported in API Gateway, no error when testing connection using openssl s_client, ...), check your API Gateway license file, this error can happened if the unrestricted option of your license is not recognized (expired license, ....)