Saving directly to zotero.org doesn't work in the current version of the Safari connector. Make sure Zotero is open when you try to save and it should work.
An update to the Safari connector should re-enable saving to zotero.org, though you'll still get better results by making sure that Zotero is always open when you try to save.
Upgrade Storage
An update to the Safari connector should re-enable saving to zotero.org, though you'll still get better results by making sure that Zotero is always open when you try to save.