Offer letter not issued

I had applied for the post of Scientific /Technical Assistant ‘A’ GROUP -B Wide Advertisement Number: NIELIT/NDL/NIC/2017/7. The recruitment written exam held on 17/12/2017 for this mentioned post at all respective centres. The result of written exam was declared on this 5/9/2018 on http://nielit.gov.in/recruitments , titled list of selected candidates. Further process for document verification I visited Punjab state centre on 25/7/2018 and I have submitted my all documents, i.e. AMIE Degree (B.Tech / BE equivalent degree from Institute of Engineers(India) , AICTE notice of the recognition of the degree , MHRD Gazette notification of recognition of the degree as equivalent to the degree of the recognized universities , 10th certificate for age verification, along with the written application. During document verification I was told that my degree i.e. AMIE degree which is well recognized by MHRD and Govt. of India was not mentioned in the advertisement. Although they accept, my documents and said we will discuss with higher authority and will inform you later. Now after several telephonic and E-mail conversations there is still no satisfying answer. Neither disclosing who and where to contact for the higher authorities which will take final decision regarding my case. Now as on 20/09/2018 other candidates who are selected along with me are getting their offer letters and joining dates mentioning to join before 31/10/218, whereas no offer letter is issued to me till date and I have been again said to wait without mentioning any specific time limit .