Query for link documents

Respected team of expert lawyers. I had recently applied for an education loan againsta a collateral security which is a flat in bhayander east. However the link documents of the flat were not registered since they were very old ( one of 1981 and the other of 1989). When asked , the secretary of the society said that the owners at that time might have not felt it necessary to get the documents registered and so they did not do so. Also in 1981 there was gram panchayat there. Also the BMC approved plan copy ifor the 4th floors is missing. Now the education loan department refused to give me a loan citing the non registration of the link documents and the missing bmc approved plan copy. Kindly advise me on the solution for this.