1556662212 error code. Having issues with syncing. I have signed in etc, tried to sync 5 or 6 times but keep getting this error. could it be my pop-up blocker?
Your socket connection to the server was not read from or written to within the timeout period. Idle connections will be closed.
This is a message from Amazon, which underlies Zotero File Storage. We've been seeing a lot of this lately, but I'm not sure why—it could be something on your system or a change in recent Firefox versions. In any case, it's harmless on its own. Just keep syncing, and it should finish eventually. You can follow file sync progress by hovering over the blue progress bar.
But try disabling all your other Firefox extensions to see if that fixes the problem.
No idea if it will help, but you can try going to about:config in the Firefox address bar, changing extensions.zotero.sync.storage.maxUploads to, say, 2 instead of 4, restarting Firefox, and syncing again.
You might also just be on a slow network connection, and Amazon might have reduced the timeout. In a future version we'll probably just retry errors like this silently.
But try disabling all your other Firefox extensions to see if that fixes the problem.