You have added a dataview on a page that requires a source entity and you did not select this.

See https://docs.mendix.com/refguide/data-sources for more information on this or follow the learning paths on https://gettingstarted.mendixcloud.com/link/path to learn more about the mendix concepts

A dataview needs a datasoruce, see: https://docs.mendix.com/refguide/data-view

and check out the Mx learning path: https://gettingstarted.mendixcloud.com/

I have the same problem, during the rapid developer course.

it says we will solve the problem later, but it seems that the specific page on how to solve it, is not present.

Does anyone know how this should be solved, during the course?

I understand I have to select some kind of input, but during the course I do not know what database or stub or anything I need to select to connect.