Client authentication failed - unknown client

Hey guys, I’m trying to install an integration with Gitlab and one of our products (Freshservice), but when we try login to Gitlab via OAuth, we get the following error:

**Client authentication failed due to unknown client, no client authentication included, or unsupported authentication method.** 

I noticed that the issue happens specifically for custom GitLab domains but not with default gitlab.com domains.

Please find the screenshot attached below. Any updates/guidance regarding this would be appreciated. Can I please receive some help to resolve this issue?