Daniel Orelius
When automation source control with Auto sync enabled is created, automation service tries to create a webhook on the GitHub repository to trigger auto sync of the runbook to the automation account. If you already have 20 webhooks in place on this repository then it will fail as it hits the GitHub limit which only allows the creation of 20 webhooks per object.
Resolution :-
To delete unused webhooks on your repository or to use manual source control.