"Please provide a valid token"

I have a webinar embedded in my website using Dowow.tv.  For the last four weeks, it worked well and people who logged into the page where it is hosted were able to put in their name and any email (i had all registration and verification turned off).  Suddenly, if you try to use the join link through any browser page, it says "This webinar is for authorized attendees only" and if you try to join through the Dowow.tv plugin, it asks for a valid token.  WTF happened??