Thanks for your reply! If you are using TestRail Cloud and are attempting to connect to a local JIRA instance, you would have the following options:
Make your JIRA instance available for connections over the Internet (I recommend talking to your IT team for this; we can also provide the IP addresses of our servers so you only need to approve our IPs for connections)
You can also install TestRail on your own local server and we can provide the necessary details for this
Alternatively you can also already use our full URL-based integration plus our full native JIRA add-on integration, as this doesn’t require any kind of TestRail -> JIRA connection. This would only be required for the push/lookup integration. So our full add-on integration would also already work in your case
Hope this helps!