While there's many reasons for the "Fabrication Job Contains No Parts" error while trying to import an MAJ into Revit, it's NEVER because there are no parts.

While it doesn't cover ALL the reasons for this message, one of the most common can be worked around with this process...

https://www.darrenjyoung.com/2021/02/09/fabrication-job-contains-no-parts-possible-fix/