...
When the app (that is installed on Jira) makes a similar call, the Jira host uses a different DNS 2. In many organizations, the (Jira base URL) proxy’s name is not configured in the DNS2, therefore the call fails throwing a Unknown Host Name Exception.
There is are several ways to resoove resolve this:
add the proxy name to the Jira’s /etc/host file.
add the proxy name to the DNS 2
...