Unable to configure gitlab plugin


I already created an issue on github for this gitlab plugin but didn’t get any response. That’s why I post this here and hope for help. Try to make this run for days now without success.

We are running Mattermost 5.21 and want to use the gitlab plugin from Marketplace. I followed all the steps from the readme and I’m able to have the Gitlab icon show up in Mattermost. When I click on it the authorization confirmation pops up from our Gitlab server. After selecting the “Autorize” button I get the following error message:
Post https://{gitlab-server-url}/oauth/token: proxyconnect tcp: EOF

I tried all different ways but just can’t find a solution or at least a way to identify the issue. Checked the debug log of MM - but no other than this entry found there.

Please help me to solve this! Drives me nuts…

Thanks in advance

Issue being triaged here: https://github.com/mattermost/mattermost-plugin-gitlab/issues/157.