Most requests from Heroku to Twitter are timing out. Heroku responded to my ticket with “It looks like Twitter has blacklisted some of our primary IPs. We’re working with them to get delisted but don’t have any ETA on when that might happen.”
You can see users discussing this issue here:
This is a critical issue for many businesses who are hosted on Heroku. Please resolve this ASAP. It is a critical issue for us and impacting all of our customers.