Flash the firmware first. But don't put the -R at the end of the command. The -R switch is to tell the phone to reboot.

Once the O/S/firmware has finished being flashed you should be returned to the command prompt in Flasher. You can now flash the EMMC. This time put the -R switch at the end of the line.

If it fails to flash on this occasion, you could try a third time, but chances are your EMMC is poopsenfartzenshitzen.

A word of warning though. I've heard rumor that Nokia are returning them as "Beyond economical repair", if the EMMC is damaged.