I got my attachments on my mac, and synced them. I can see these pdfs on my ipad, but I cannot download them to view them.
It says:
"The attached file is not available on the webDAV server. Please check that the file has synced on the device where it added."

How can I make sure that all the files have been synced? since I've clicked the syncing button several times, and reopened zotero on my ipad again and again, this just doesn't work. I download the books I attached before and succeeded, I just don't know why these new books failed me so many times.