Did you follow the step below after you sent the firmware to the 990?

18. Reset the unit by pressing the front panel “Enter” (center of circular key pad) and “Menu” buttons simultaneously and holding them unit SYSTEM RESET appears in the front panel display. Release the buttons when the message appears and note that the Model 990 will turn off and return to the standby mode after a few seconds.

I forgot to do this step and the device came up with the old firmware. When I reread the instructions, I realized that I missed this part...