Can't Generate time machine archive

I downloaded plugin Time Machine 2.0.03 to back up to my Dropbox and it is active but it will not generate my archive. I keep getting an error message.
I have the correct email and password and have refreshed it many times.
I am using 3.4.2 WordPress. Is there another version of Time Machine that I need to use or can you give me some troubleshooting tips.
My website is: http://www.rivcosquaredance.com

Thanks

http://wordpress.org/extend/plugins/wp-time-machine/