Refund of agreement amount on cancellation

I had paid an advance amount for a flat in Bhubaneswar. Agreement was done on the basis of the payment in December, 2020. The person taking care of my sale from the builer's side suggested me to apply for the home loan in SBI main branch. However, the bank rejected the loan saying that RERA approval certificate is mandatory for this. RERA approval is still pending for the project. four months passed. Then I approached LIC HFL for the loan who again denied the loan stating the same reason. Now I applied for cancellation of the agreement in April, 2021 with no other options left. Now the company is saying that 10% of the agreement value shall be deducted from my refund value. I understand that in case the buyer is at fault, the forfeiture of 10% amount is logical. But in this case, the fault was completely at the company's end as they do not have the RERA approval yet. I have tried to convince them the matter but they are so adamant. This has been a horrible experience for me with not a single fault of mine. What should I do in this case? Please suggest whatever is possible. Thank in advance!