Impossible to make columns for fields

Hello,

I can’t arrange my fields in multiple columns (2 in fact).
In the description of the plugin, it’s written : “Multiple field layout options. Arrange your fields in two, three, or a mixture of columns.”

But I can’t click on buttons in the plugin (1/2, 1/3….).

How can I do ?

Thanks for the help.

https://ww.wp.xz.cn/plugins/visual-form-builder/