webhook add error 404 "Not Found"

Bug report

Current behavior

/gitlab subscriptions add Group returns

Successfully subscribed to Group.
A Webhook is needed, run /gitlab webhook add Group to create one now.
Note: We are unable to determine the webhook status for this project. Please contact your project administrator

however, running /gitlab webhook add Group I get POST https://SELF-HOSTED-URL.example.com/api/v4/groups/241/hooks: 404 {error: 404 Not Found}

Expected behavior

/gitlab webhook add Group completing succesfully

Environment

• Self-hosted Gitlab Instance v18.1.1 ce
• Self-hosted Mattermost Instance v10.9.1 E1
• GitLab Plugin v1.10.0

Steps to reproduce

• follow the setup instructions
• Verified my user is included in the group
• Enabled Private repositories in the Plugin Configuration, Child Pipeline configurations and Code Previews for public and private repos
• perform on a private mattermost channel

1. /gitlab webhook add Group
2. /gitlab subscriptions add Group

Additional info

It seems I also cannot add just my repo to the subscription.

I've tried with:

/gitlab subscriptions add Group/Group Example
/gitlab subscriptions add group/group-example

The project Repo is named like "Group Example", and it looks like group/group-example in the URL

Use /gitlab webhook add Group as the entry point and reproduce the POST to /api/v4/groups/241/hooks against GitLab 18.1.1. Compare the request with the GitLab group webhook API behavior. Done means the command creates the Group webhook successfully and the subscription flow no longer reports an unavailable webhook.