I’m not really sure what the problem is based on the info collected here so far, and I can’t reproduce the problem in any tests. What I know so far is that Publicize is indeed working for scheduled posts, but it sounds like it’s not working for some of you but there’s no trend I can see so far that might give us a clue as to what’s causing that problem on your side.
Are you guys also using the email subscription service in Jetpack? If you are, can you tell me if the email messages get through but the Publicize messages don’t? Also, if you report in about this, please note exactly which services you’re having trouble with, whether Publicize works for you without scheduling the post, and some basics about your server setup if you can provide that, and anything else you think might be worth tracking as a possible trend. I noticed two of you mentioned using nginx, but the others didn’t say what kind of web server they’re running. I’m just looking out for any trends (not sure exactly what yet), so the more details the better. What we really need are steps to reproduce the problem reliably in order to even start to try to fix it.