Why I cannot enable the smart embed option?

I can't enable this, it's always grayed out. Why?

This is only available for card forms, all the forms in your account are classic forms, please kindly check carefully the guide as this is explained there, it's also provided the guide to switch the form layout. 

Here's the direct guide so you can change the form layout: https://www.jotform.com/help/493-How-to-Change-the-Form-Layout 

Thanks.