unknown email

Hi, It's been a while now that i am not using prezi anymore but today I tried to log in and It seems that i can not logg anymore. SO i tryed to reset my password and the website doesn't seems to know my email address. Because the following message appears: Unknown email. 
My account is this one: http://prezi.com/user/valentindesmarais/

Thanks for your help!

Valentin