cooperative society plot

Assalam o Alaikum.
Sir, we had a plot in cooperative society for which the payment was completely done in 1989..we were abroad at that time since then we never received any notices from the society for any instalments, dues etc, however, they committed to giving us lease n possession which is still pending. We shifted to khi 2005..visited the plot, there was no address of society written accept their title..
One month ago I traced their office address from an estate agent and when I visited they said the plot has been cancelled because we didn’t have contacted them for 30years n we had some dues of 52500( maybe of maintenance etc they didn’t clarify).
Please suggest Sir

Regards