I am running Zotero stand alone on a Mac, using Sierra 10.12.1. When I save a citation with PDF (Safari), the file will not attach (gives me the dreadful red X). This is happening on group library as well as on my own library. I have installed Zotero on windows based computer using firefox and it won't sync with my library. This issue is persisting with some of my colleagues using both El Capitan on Mac and also Windows (chrome). I have checked that my settings are all good, have checked boolean settings as well to no avail. Thinking this may be a connector issue, so re-downloaded connector, still not working. Help??