Hi Thirumala,

The cause for the above issue is the relevant certificate of the backend which you are trying to invoke, is not available in the <MI-HOME>/repository/resources/security/client-truststore.jks file. So to make sure that the backend certificates are available inside client-truststore.jks file, You can take an output of that file and compare it with your endpoint’s certificate details.

Please use the following keytool command to get the output of the client-truststore.jks file.

keytool -list -v  -keystore client-truststore.jks

Please note that If the backend is having a certificate chain, that chain should be available in the client-truststore.jks file. You can get the endpoint’s certificates using the OpenSSL.

openssl s_client -showcerts -connect <hostname>:<port>

If the relevant certificate is not there please import the public certificate of the endpoint to the client-truststore of wso2 MI.

Further, please note that you need to restart the MI server to take certificate changes/imports to take effect.