Bank refusing to give loan on a mortgaged property to another buyer

We purchased a property in Santiniketan, Bolpur, West Bengal in 2009. We took a home loan from SBI, Santiniketan. Now recently we advertised for selling it and one person showed interest to buy it. He is willing to take a loan as well and approached the same bank where this property is mortgaged. However, bank is not ageering to finance this property citing various reasons. Few points to be noted that: 1. The land conversion is not done for this property - it was not done in 2009 also. It was classified as 2. Agricultural Land. The same classification is still there. 3. We have done mutation and transferred the property in our name. 4. We have been paying Khajna, Tax. 5. There is a valid registered sale deed for our purchase. 6. Bank is asking for conversion to be done. However, in that particular area in West Bengal, due a court case, no conversion is allowed till the case is settled. In view of the above, when the bank supposedly verified all above points and gave the loan in 2009 and as the loan is still active, how can they refuse to entertain a new loan on the same property? If they had given loan when the property didn't have proper classification in 2009, can they refuse now on the same gound? It clearly shows that bank didn't do proper due-dilligence in 2009 and misguided us in believeing that everything is ok with the property. Now, in 2024, we are suffering from this negligence and oversoght on bank's part. What should I do?