Hello Martina,
that probably has to do with the parameters of the menu item.

First: do you have contacts in the Joomla! contacts' component? (just asking, most of the time, believe it or not, this is the problem)

Second: what did you select in the parameter section? (can you post a screenshot of your basic parameters?)

Thank you!

No, the module and menu item are 2 different entities. Having both on the same page won't help.

Once again, can you post a screenshot of your basic parameters of the menu item? Thanks

Ok, you have no contacts showing because of the meta keywords field. Empty it out and you will have results.
If you need keywords, they need to be coma separated and the contacts need to have them in their profile.