You need to update your Rhino. The version you are using is a version before “RebuildNormals” existed in Rhinocommon, that is why it is telling you it doesn’t exist.
I would like to suggest to the ShapeDiver team, that any possible Rhino and GH version requirements to be added to the documentation and the component.
I agree that the documentation and the model should include a note about the minimum Rhino version it is compatible with. We will update it accordingly.
Just keep in mind anytime you get a message that something couldn’t be found it is a good sign that it’s time to update. It could also mean that the method is misspelled or you are missing an assembly reference. In this case it is a version thing.