The following looks suspicious (although I'm not a web development expert):
The return type of the method is an ActionResult.
Are you sure that the View function accepts a string (i.e., "About"), and that it yields an ActionResult?
Alternatively, cosider the following:
d.Enroll_ID = ((Excel.Range)range.Cells[row, 3]).Text;
The Text property will return a string. Is the Enroll_ID an int? Perhaps that is what is causing the problem. And are you sure that that particular Excel cell can't contain anything other than a numeric string?
The same is true for other properties on the 'd' object, like Date and Time.