Netlink HG323RGW Firmware not updating

Messages
1
Location
Kerala
ISP
BSNL FTTH
I am unable to update the Firmware in Netlink Single band ONT.Though i upload the firmware file(Dwnld from Netlink website) and reboot,the version remains same after the process.Have tried with 2 recent update files,but no luck.Current FW version - 1.0.35-210325

Did someone face this issue before?