Problem with single register form

Hi,

I am using RCP VAT plugin.
It works well with these RCP shortcode : [register_form] or [register_form ids=”1,2″]
but doesn’t work witt a single one like: [register_form id=”1″]
In this case, every amount line display 0.
Do you have any idea of the problem?
Thnks for your help.
Best