Checkboxes are not showing

Hi,

I am using the ninja form as a registration form on my website. However, I found the checkboxes are now working as the “boxes” disappeared. May anyone help?

Screenshot is provided below
https://drive.google.com/file/d/0B9iadpGqZ8SnZEcyVDJ3ekpNRWM/view?usp=sharing

Thanks!

https://www.ads-software.com/plugins/ninja-forms/