HTTP ERROR 500 while invoking a Third Party REST API

Hi,

I am trying to invoke a REST API (with Basic Authentication). The Basic Authentication Digest is coming out correct however while initiating the call I am getting this error:

Could not connect
HTTP ERROR 500

Problem accessing /service/proxy. Reason:

java.security.cert.CertificateException: d2:CN16:...:Go Daddy Secure Certification Authority2:io12:"GoDaddy.com3:iou42:http://certificates.godaddy.

I have added the property in Config file
<global>
<property name="allowedDomains">*.mydomain.com</property>
</global>

AND also added *.mydomain.com" in the Admin panel in ZCS (7.2) under Configuration > Class of Service > default > Advanced Tab

Additionally the code is as follows:
AjxRpc.invoke(, feedUrl, hdrs, callback, false);

ignoring the first parameter as this is a GET request. I also tried adding a null / empty string but none of them helped.

Any help would be much appreciated!

Thanks