I just set up the integration with Gitlab in my organization and everything seemed to work fine.
Now all webhooks return a 409 which causes GitLab to end up disabling them.

After successfully setting up the integration between GitLab and Sentry, webhooks may begin returning 409 Conflict errors. This status code indicates a conflict with the current state of the resource. For example, this could occur if Sentry detects duplicate or conflicting data in the webhook payload.

Please reinstall the integration, as it resets the webhook configuration and resolves potential conflicts in the state of resources.