When you double-click on an item or attachment in Zotero, you mean? (Single-clicking just selects items.)
Zotero simply launches the file via the OS, so if that's not working, there's not much we can do. What happens if you use right-click → Show File and then double-click on the file in Finder?
Restart your computer and try again. If you're still having trouble, if you provide a Debug ID for double-clicking on an item and getting this behavior we can take a look.
Zotero simply launches the file via the OS, so if that's not working, there's not much we can do. What happens if you use right-click → Show File and then double-click on the file in Finder?
Restart your computer and try again. If you're still having trouble, if you provide a Debug ID for double-clicking on an item and getting this behavior we can take a look.