Hi Rachel, it's really difficult to help without being able to test the file.

Does it open in CAD Assistant? https://www.opencascade.com/products/cad-assistant/

Another thing you can try is using CAD Exchanger to convert it to a Rhino v5 .3dm file:
https://viewer.cadexchanger.com/

Also another way to test it is with SolidWorks eDrawing viewer:
https://www.edrawingsviewer.com/download-edrawings

- Michael