Registration Button not working

I've just set up a series of meetings for which I'm requiring registration.  But the registration button isn't working.  When visitor completes the form, and clicks the button,  nothing happens.   

This seems to happen on mobile (ios, at least), and on various browsers from my mac.

interestingly, when i'm logged in to zoom.us, the button does seem to work, but not otherwise.

HELP!