[Plugin: cformsII – contact form] Page not found error

Hi guys

Bit of an odd one that I just can’t figure out so hoping for some expert help here 🙂

I’m trying to use CformsII – the plugin installs fine, the backend works fine, but when I try to put a form in the page by clicking the button from WordPress I get a 404 error … the popup appears and the code inside is a 404. It’s bizarre.

Can anyone help here?

Many thanks in advance.