Do your users open workbooks that ask if they want to update links? Do they know what to answer? This is common when you send workbooks to third parties with formulas linking to other workbooks.
They don’t have access to source data, so don’t make them choose. In a workbook with external links, on the Data tab, in the Connections Group, the Edit Links button will be active. Click it and then the Startup Prompt button in the bottom left. Choose whether or not the data attempts to update and whether or not the user has to take an action.