Prezi application - No connection to prezi.com

Hello,

My company wants to purchase the Prezi Desktop and before purchase it, we want to try and be sure that it can be used without Internet connection.

I have downloaded and log in Prezi Desktop when I have Internet connection. However, I try to log in when I have no Internet connection, I take an error like as "No connection to prezi.com" and can not log in.

I have read in your conversations that after first time log in, you don't need Internet connection. However I cannot log in without Internet connection. Could you explain that clearly, do we have to use it with Internet connection ? If not, why I can not log in Prezi Desktop.

I am waiting your responce in a little while.
Thanks,
Sincerly...