You have connecting web parts on page passing values between web parts on your SharePoint page, sometimes you see an issue where the page does not load, it is hard to make the connection, page becomes unresponsive and may also see java script errors similar to
Message: ‘SP.Ribbon.PageState’ is null or not an object
Add each web part; select ‘save and close’ option. (If that doesn’t work, close the browser and open the page again).
Open the page again, go to the web part, click on the drop down at top right corner, click ‘edit web part’. Select the same drop down again and click on ‘Connections’. Make the required connection, save and close.