You are unable to add a repository to a Trigger. More specifically, you are unable to add a webhook to your repository.
You may see the following error:
Failed to add Trigger to GitHub
You may also see that the trigger is created, but marked as Unverified. Clicking on the "Verify" button again still fails to successfully verify the trigger.
The Git context does not have permission to modify or access webhooks on the repository.
Check the user or token used for this git integration. Ensure that it has the appropriate access to create webhooks. Please check our git integration documentation for additional details on which permissions are required for your specific git provider.