Issue with GitLab-Slack Integration for Specific Project

Problem

I am the administrator of our company’s Slack workspace, and I have successfully set up numerous integrations with Slack apps without encountering any issues. However, I am facing difficulties setting up the integration for a specific project:

• When I attempt to test the settings in the GitLab for Slack app settings page, I receive the following message: “Connection failed. Check your integration settings. GitLab for Slack app must be reinstalled to enable notifications.”
• Unlike in other projects, there is no reinstall button at the top of the page. Instead, I have a button labeled “Install GitLab for Slack app…”, indicating that the integration is not installed, although it is.
• When I try to reinstall the app and authorize GitLab and Slack, I encounter a 422 error message stating that my request has been rejected.

I have attempted the following without success:

• Using multiple browsers.
• Enlisting another Slack administrator to attempt connecting the app and authorizing it.
• Waiting for several weeks.
• Removing the GitLab app from the Slack channel, reinstalling it, and reauthorizing it.
• Setting up the Slack app integration at the Group-level integration. In this scenario, the integration works flawlessly with other projects within the group, except for this specific project.
• Removing the app from the Group-level integration.

In the meantime, we have successfully created new projects and set up Slack apps without encountering any problems.

What steps can I take to resolve this issue and enable GitLab notifications to the Slack channel for this project, without deleting the repository?

The project is private and I am using GitLab SaaS (version: GitLab Enterprise Edition 16.11.0-pre 22d5b082dc5).

I have this exact same problem. Many projects with integration configured. New project will not work. I select “Install GitLab for Slack app…” button, it goes to Slack to confirm permissions and I select “Allow”, goes back to GitLab and gives a “422: The change you requested was rejected” response. I am an administrator for both our GitLab account and our Slack account. Doesn’t make sense. Hoping this gets fixed soon; Slack notifications are critical to our workflow.

We have this exact issue as well. Other projects in the group have the Slack App integrated and issuing push notifications to Slack without issue. Meanwhile for one project of mine:

422 response when trying to install.

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Yet on the Gitlab for Slack App page, it is labeled as Active.

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If I select Use Custom Settings on the top right then Test settings on the bottom, it returns a Connection failed... response.

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There is no way in the UI to uninstall/reinstall this App. I have Maintainer permissions in this project, but i’ve also had a user with Owner permissions attempt the same steps and they receive the same responses. No idea what’s going on and this is very frustrating.