Can’t publish post using ajax

To those who are experiencing the same issue, there are few steps to take to determine the culprit.

1. Create posts manually in the WP Dashboard area (set it to future)
2. .. and manually publish (look for the error in the log).
3. step 1 and trash the post, in the Trash, try reverting that post (this generally create a log, and a log is all we need in this case).
4. Check for any plugin which filters the post publish.

Hope this helps