the popup of term and condition is empty

-- HikaShop version -- : 2.5.0
-- Joomla version -- : 3.4.3
-- PHP version -- : 5.5.24

Hello
I have a web site with hikashop on line but just now I have noted that there is problem with link acept term and condition.
When I click on that, it looks as open a popup but without anything it is empty.
I checked the configuration and the the correctarticle is selected..
ON the page of the checkout the link of acept term and condition is:
dominio.it/pagamento/checkout/task-step/step-2.html#

What could be the problem??
THanks
Frank

I actived mootools for popup in configuration>display and now it looks working but I have to check if everyting is ok with other popup.
I will let you know

Thanks