Succession certificate for Pune apartment flat

My mother (69) and my maternal cousin brother (deceased in 2019) son of my late aunt (deceased in 2018) both Mumbai residents are currently joint owners of 2 adjoining flats in a Pune based apartment building (not CHS). We presently not able to trace my cousin brother's flats nomination nor Will document. So our Pune apartment secretary/office bearers have requested us to get succession certificate in order for them to transfer 50% share of my cousin from both the flats ownership to my mother's name. Background of my maternal cousin: My Aunt marriage: Feb-1985 My cousin DoB : Jul-1986 My Aunt Divorce Date : Jul-1994 Flat #1 & #2 Buy Date : Jun-1995 My cousin's name change: Apr-2015 My Aunt Died : Jul-2018 My cousin Died : Dec-2019 Note: both flats were purchased in 1995 after my maternal aunt was divorced in 1994 and her 100% ownership was transferred equally to my cousin and my mother after her demise in 2018. My maternal Cousin was Never married and had no children nor any siblings. Post divorce in 1994 My cousin's father has never been in any contact nor till date his whereabouts were ever known to us. My cousin dropped his father's name and officially changed it with his mother's name as his middle name in 2015 (affidavit+newspaper declaration). Problem statement: We've filed for succession certificate since 2021 but court keeps asking us to give 100% of my cousin brothers ownership I.e. 50% combined of both the flats present ready recknor value to my cousin's father or same amount deposit in court or accept to give same if he/legal heirs claims in future. What went wrong here in filing case and what we should we do now next to get the succession certificate safely in my mother's name? Or is there a legal alternate option available other then succession certificate? *My mother's Family tree consists of Level1: Father (deceased) + Mother (84) Level2: (i)My mother(current 50% owner), (ii)my aunt1(Deceased), (iii)my aunt2*(Deceased) & (iv)my uncle (58) Level3: (i)2 children, (ii)3 children, (iii)1 child* (current 50% owner deceased), (iv)2 children