I have Omnibus Gitlab and Mattermost installed on two separate machines. Both use HTTPS with Let’s encrypt certificates and HTTPS works fine.
The problem is that when I use SSO with Gitlab, Mattermost returns the dreadful error: Bad response from token request. The log file is the following (note how the details section is empty!):
[EROR] /signup/gitlab/complete:AuthorizeOAuthUser code=500 rid=o9nzr1yjbtr15xqi5hy8pwssnh uid= ip=IP_ADDRESS Bad response from token request [details: ]
I have tried including Let’s encrypt certificate authority as explained in other posts, etc. but it did not help. Any Suggestions? Would love to solve this issue.