Github will restore their service hooks temporarily today (see https://www.githubstatus.com/incidents/kq75qp7try8t
) but they will be deprecated completely on January 31st, 2019.
Please update to use our new GitHub integration, see: https://www.pivotaltracker.com/help/articles/github_integration/
Note: If you use GitHub Enterprise Server (the on premises version of GitHub Enterprise) you will not be able to use our above new integration yet, however Github will not be deprecating their service hooks in that version for at least 3 months.
For questions meanwhile, please email firstname.lastname@example.org