Yea, we did see issues with a small number of users behind a symmetric nat, which is usually found at work. We're looking into ways around this and we're open to suggestions :)

However, you may still be able to send files back and forth if both users are inside the firewall.

I tried that, but I cannot even enter my username. After entry, it won't permit me to click on the 'Continue' button. It does not seem to be active.