An error occurred uploading to the app store with no error code
I had the same problem this morning, you can try to open the terminal and run these commands:
cd ~mv .itmstransporter/ .old_itmstransporter/
It worked for me.
Go to Preferences > Network > Advanced > Proxies and make sure "Auto Proxy Discovery" and "Automatic Proxy Configuration" are checked but none of the other proxy options are checked. I had to uncheck "SOCKS Proxy" option to resolve the issue. Found this solution in a comment of this thread.
The only thing that helped me was to use Transporter (from the Mac App Store: https://apps.apple.com/us/app/transporter/id1450874784?mt=12). Export with the export button on the failure panel to a directory. Login, then open the *.ipa with Transporter and the upload works.