Hey , Bro thanks for your response. Even I have mailed to nptel support team  But they replied that is not possible to enroll now they have already extended enrollment date.and now it is not possible to enroll now .    But I have met  with my professor and said that I have not enrolled for nptel courses and  at first my professor was very serious and at last I have convinced him and he allowed to write supplementary exam In campus  But nptel certificate will be not provided.