No, there are no error messages after klicking on “import messages” (0 comments has been imported). There is also no error in the logfile.
Example: This article https://bit.ly/1HCSW30 has three FB comments. 1 comment and my answer to it, and 2nd comment. 1st one and answer are imported, 2nd comment is not in the blog but exists on FB. Import manually doesn’t work. https://on.fb.me/1HCT0Qv