ecmetrics

@sirector REST_API is another plug in? if not, How do I activate it?
@takayukister that was exactly how the problem started. Someone deactivate all plugins. I know you could give a better solution.

Thanks WPyogi for your prompt help. The idea is if I can have the landing page on WP blog. For example, the reader will see a brief description of the white page in the blog and he would click in the link to download the complete white paper, but in order to do that , he/she will have to complete a small form with their personal details (email, name, last name , etc), all this inside the same WP blog.

Is that possible?

It work perfectly, thank you so much for your help!

YEs!!! you are great, thank you.