Why I get no results in my Content search Webpart in Office 365? The query Shows me results by testing, but not in the site.
What license do you have?
If you do not meet the license requirements which is any of the Office 365 Enterprise plans, you will see the webpart, be able to add it to a page and create a query and get results while testing it in the dialog, but it simply won't work in the site.
Q: Which SharePoint Online plans include the search-driven publishing features?
A: The Content Search Web Part and Cross-site Publishing are available for Office 365 for Enterprise plans. Specifically, these plans are: Office 365 Enterprise E3 and E4, Office 365 Education A3 and A4, Office 365 government G3 and G4, and Office 365 Enterprise E3 for Nonprofits.