Hmmmm.... I just posted a video of how to do the FIRMWARE update. I was thinking of also including some tips on what to do if things go wrong, but didn't have the time to include it.
I'm guessing the problem is with your micro SD and the ability of the ST16 to read it properly. You can easily check to see if this is the problem. Insert your micro SD into your ST16, power on the ST16. After it boots up, tap PAD in the bottom left corner of screen. Then when in the green screen tap the bottom center circle with dots in it. Next look for the APP called something like FILE MANAGER (yellow file folder). Start up that App. Now look at the top left of the screen... you should see a super tiny picture of your micro SD card. Drag your finger from the top of the left hand screen down over that tiny icon. You should then see a status of your Micro SD. If it says there is a problem with the micro SD, then that is your problem. You can try letting the ST16 format it and then try again, or use a different micro SD.
If the above is not the problem, then it's just a simple case of the firmware update file not being in the root directory of the micro SD card.
Good luck.