The firmware updates for your BCD996XT are downloaded through the BC_VUP Firmware Update process.
To check for the version on your scanner:
Menu Key ---> Settings ---> See Scanner Info ---> Firmware Version
The changelog for the BCD996XT firmware updates is here:
Have you unzipped and installed the BC_VUP Firmware Updater on your computer?
Are you using the front port on the BCD996XT for updating the firmware?
Have you verified that when you connect the cable to your computer that a valid COM port has been assigned to it? Look in the Windows Device Manager under "Ports (COM & LPT)" to check for the COM port.