You may see the following error message "The friend server “xxx.xxx.xx” could not be contacted”. Possibly with an additional error message "failed to load resource: the server responded with a status of 500 ( )"
Get the atlassian-jira.log and verify if the following message appears in the log file: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to
There is a good article on Atlassian identifying the issue you may be experiencing.
There are several ways to establish trust relationships and certificates and it’s best to share this article with your network and Jira admin.
Once your network is good then you can proceed to configure the connector.
Perform a similar task from DNG and verify you can get to the rootservices on Jira. If you don’t, you should be able to look at the rm.log (available from the admin page → debug → logging) and you should see messages when you attempted to friend. If you want our help interpreting the results of those messages let us know. We may see specific configurations for trusts as well as TLS levels from the configuration of your ELM environment as well.