a zoho form says "invalid entries found" if its html code is embeded as an iframe

[Pelix1000]

I created a zoho form with a public address, when is load it from its URL works fine, any browser. Now I´m trying to embed its html code in a webpage body, everything seems well until I click submit button, a message appears saying "Invalid entries found".

Here is the form URL: https://forms.zoho.com/smilenavas/form/Prueba

It is expected that form can be submitted either load it from its url and from a webpage which contains its html code embeded.