We set up a application link between our JIRA server and our Bitbucket server. Both run on different host in the same network. The link from JIRA to Bitbucket works perfect. In the other direction I'm shown an 503 error.
In the other direction I'm shown an 503 error (service unavailable). If I log onto the Bitbucket server, I can open our JIRA instance.

What can I do to resolve that? Why is it only working one way?