I have installed Mattermost (via the omnibus installer) to the latest version ( 8.1.1-ee) and its alive and kicking. However when I login as a Gitlab admin user I get the following message;
Signed in successfully.
An error has occurred
Client authentication failed due to unknown client, no client authentication included, or unsupported authentication method.
We have a proxy server running which is forwarding to both the Gitlab & Mattermost instances and they are installed on the same machine.
I have tried to uninstall the application and reinstall ( following the documentation) and done a number of gitlab-ctl reconfigures but nothing helps.
Can anyone suggest any additional things I could try.
Thanks in advance