Student conflict

Can anyone provide any insight... We have a 6th grade student who has been enrolled at Porter since Kindergarten. She is not showing up in the teacher's class roster or in our list of Porter students when I do a student search using her ID#. She DOES show up in our Building Census derived from Pentamation. When I tried to add her to our list of students (using her ID#) I get the following message: "A duplicate user was found within the district. You will not be able to add a new student with this id. Please check to make sure the id entered is correct" I do not have rights to search outside of Porter. The only thing we found that was wrong in Pentamation was that the student's grade was listed as "UP". This was corrected by our secretary. At any rate, I can't assign her to her class. If anyone can help please let me know. Teresa Sauro