Open your worksheet and click the Find Broken Links button on the Ablebits Tools tab. Check Broken only if you want to see only invalid links. To get a list of all links, click the Find links in this workbook button. The found links will be shown on the add-in's pane including the reference path and the linking cell or cells.
To fix the reference, right-click it, select Edit, and enter the correct worksheet name or cell name. To change the reference source (linked workbook), click the ellipsis button next to the workbook name, and then choose the right file.