Error while retrieving JIRA metadata

[Adrian Ohler]

When linking a Confluence page with a Jira issue and clicking on "1 JIRA link" there is this error message:

"Unable to retrieve JIRA metadata. Unknown error encountered while retrieving JIRA metadata. Please check the logs."

The log file looks like this:

2018-08-02 09:08:44,787 ERROR [JIRAMetadataPlugin:thread-3] [metadata.jira.helper.JiraMetadataErrorHelper] printError Unknown error encountered while retrieving JIRA metadata. Please check the logs.
 -- referer: https://confluence.domain/display/site | url: /rest/jira-metadata/1.0/metadata | traceId: 1d07ce7ea1819cb7 | userName: useruser
org.apache.http.client.ClientProtocolException
 at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:186)
 at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
 at com.atlassian.sal.core.net.HttpClientRequest.executeAndReturn(HttpClientRequest.java:103)
 at com.atlassian.plugins.rest.module.jersey.JerseyRequest.executeAndReturn(JerseyRequest.java:131)
 at com.atlassian.applinks.core.auth.ApplicationLinkRequestAdaptor.executeAndReturn(ApplicationLinkRequestAdaptor.java:53)
 at com.atlassian.applinks.oauth.auth.OAuthApplinksReturningResponseHandler.handle(OAuthApplinksReturningResponseHandler.java:45)
 at com.atlassian.plugins.rest.module.jersey.JerseyRequest$2.handle(JerseyRequest.java:134)
 at com.atlassian.sal.core.net.HttpClientRequest.executeAndReturn(HttpClientRequest.java:104)
 at com.atlassian.plugins.rest.module.jersey.JerseyRequest.executeAndReturn(JerseyRequest.java:131)
 at com.atlassian.applinks.core.auth.ApplicationLinkRequestAdaptor.executeAndReturn(ApplicationLinkRequestAdaptor.java:53)
 at com.atlassian.applinks.oauth.auth.OAuthRequest.executeAndReturn(OAuthRequest.java:84)
 at com.atlassian.applinks.core.auth.AbstractApplicationLinkRequest.execute(AbstractApplicationLinkRequest.java:114)
 at com.atlassian.confluence.plugins.metadata.jira.service.JiraIssuesMetadataDelegate.getGroups(JiraIssuesMetadataDelegate.java:58)
 at com.atlassian.confluence.plugins.metadata.jira.service.helper.SingleAppLinkMetadataHelper$2.call(SingleAppLinkMetadataHelper.java:133)
 at com.atlassian.confluence.plugins.metadata.jira.service.helper.SingleAppLinkMetadataHelper$2.call(SingleAppLinkMetadataHelper.java:125)
 at java.util.concurrent.FutureTask.run(FutureTask.java:266)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 at java.lang.Thread.run(Thread.java:748)
Caused by: org.apache.http.ProtocolException: Target host is not specified
 at org.apache.http.impl.conn.DefaultRoutePlanner.determineRoute(DefaultRoutePlanner.java:70)
 at org.apache.http.impl.client.InternalHttpClient.determineRoute(InternalHttpClient.java:124)
 at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:183)
 ... 18 more

It's the same error as in here:  https://jira.atlassian.com/browse/CONFSERVER-46514

But it's not the same cause. In this case the linked Jira issue is accessed by a licensed user, yet it still shows the same error message. The link inside the confluence page is fine. It's only the linked JIRA issues button that's not working.

Do you guys have any idea what's causing this? Is it possible to somehow configure the Jira metadata plugin? Thanks in advance!