Web Page Composer - Cannot view the iviews dropped into my webPage

Hello,

I'm a beginner of Web Page Composer.

I'm trying to add some iviews to a webPage, I'm able to drop them into the page but they are not shown.

Generally after that I drop the iview into the site content, it collapse in a row. It result to be empty (I cannot remove the iview added and neither see it inside the site content) but I cannot add other content into it.

Other times appears the "Error Runtime Portal" (tipical red error message).

Am I missing some configurations??

Thanks, best regards