How can I sale my Leasehold Co-operative Flat

I am a NRI (Foreign Citizen), living Europe since over 44 years. For my last life settlement, with a dream I was became a member of a Housing Co-operative society with eight members (For a Stand alone G+4 Bldg.) at Salt Lake City, Kolkata on 1996. Later we have have allotted a plot on 1997. As it was not possible to perform all necessary formalities, I've appointed a "Power=of-Attorney" with a power to perform all type of necessary related jobs which was duly registered with Judicial authority. Gradually it has come to my noticed that out of eight members five of the members has sold their flat due to various reasons but till I continued my membership by paying all the necessary dues and obligations to different agencies related to the Building/Co-operative society. Few years back, when I have visited India, I came to know the existing Co-operative Society is almost inactive, no AGM held since years ,no audit reports has been submitted to appropriate authority and the Building has been "Dipped" by almost 4-5 inches and No maintenance of the whole building & it's almost in a devastating condition, As I've developed with different age related physical problems and not in a good physical condition I give-up my idea to settle India for last of my life and intended to sale it but there's lot of hassles as it's a 999 years lease property also No active Co-operative bodies, also requires a permission from Govt. of WB by paying a lump-sum amount. Consequences on the above How can I get rid off and sale my said property?