Seeing All red x’s in your mapping when exporting from Revit?
Initiate the Create Repository command in Revit.
Click the Match All button at the bottom of the section export mappings dialog.
In the dialog that opens click the browse button to open the Select ISM Section Tables dialog.
Select the table shapes that corresponds to the Revit families in your model.
Click OK twice.
That should map everything except possibly some custom parametric shapes that might be in your model.
Mapping Parametric shapes for exporting from Revit