Society not granting membership due to claims that GPA is invalid

purchased house in nsg sas society greater noida from allottee /member in 2005 at that time allottee executed stamped and registered sale agreement at my name and stamped and registeredGPA at the name of my wife. after completing all needed formalities allotee applied in society for NOC to execute the transfer deed at my name. tthis transfer permission was approved by executive committee of society and AVAS EVEM VIKAS PARISHAD LUCKNOW society issued NOC for transfer in April 2011 and fully stamped and registered GPA holder (my wife) applied for TMO IN GNIDA and after issuence of TMO transfer deed was executed by GPA holder (my wife) at my name.in April 2011 and issued mutation letter later on in 2016. Society after getting transfer deed at my name asked for some papers to coplete formalitier for membership transfer. Now society refuses for membership transfer saying GPA sale is not valid.