Flat transfer in name of my mother after my fathers death

My father expired in Nov 2024. We stay at Sanpada, Navi Mumbai. The flat was purchased through CIDCO. My father and mother both are the owners of flat. He did not leave any WILL. When we approached our Society for flat transfer in name of my mother they told us that they require Heirship certificate. For Heirship certificate we approached one lawyer. He said as my father was govt servant no need of applying through court. So we applied it through Tehsildar. And his office was located at Thane. The lawyer completed the procedure and has called us for collecting the certificate. He said the certificate should be submitted in Society office and they will do the needful. One of my friend who is also lawyer told me just submitting the certificate in Society is not enough. You need to go to CIDCO office and submit the application and necessary documents. It seems your lawyer did not told you about this. Maybe he is from Mumbai side. In Navi Mumbai without CIDCO formalities flat cannot be transferred to your mothers name. Kindly guide me as I though whatever fees I paid to lawyer was including everything i.e. flat transfer in name of my mother