Max Date Returning Null for All Date Fields

I'm trying to pivot column values to column names, and populate their fields with the most recent date in the DueDate field. The code I have is returning NULL for every field. I'm not a DBA, but I need to get this done. My code is below. Thanks!

selectPatientGUID,Bordetella,[CanineDistemper],Rabiesfrom(selectPatientGUID,ReminderName,DueDatefromdbo.idvPatientReminders)dpivot(max(DueDate)forReminderNamein(Bordetella,[CanineDistemper],Rabies))piv;