Install by downloading the latest version.
You can use the .xpi file from the link above to install in the Zotero standalone app:
Import folder of attachments into a collection hierarchy. Click the green "+" button above the item list, and select "Add files from folder"
My time is extremely limited for a number of very great reasons (you shall have to trust me on this). Because of this, I cannot accept bug reports or support requests on anything but the latest version. If you submit an issue report, please include the version that you are on. By the time I get to your issue, the latest version might have bumped up already, and you will have to upgrade (you might have auto-upgraded already however) and re-verify that your issue still exists. Apologies for the inconvenience, but such are the breaks.