The “Publicize” option stopped working for me—the first time I noticed it was this Friday. Usually I schedule a post, tick the option to publicize via Twitter, and at the scheduled time, the tweet goes out. The post on Friday and again this morning didn’t send out an automated tweet, even though the box was checked.
There are many threads on Publicize issues pertaining to Facebook. There have been 2 days or more of people posting them now. I assume something has changed at Facebook and I’m thinking maybe your issue may be related.