I did follow the directions, multiple times. I don't even get the option of selecting a card because I get eh error right off the bat.
You'll need to be a little more specific.....
When, exactly, do you get the error...
When you turn on the scanner?
Does the scanner get into the "mass storage" mode..... or do you get the error when you try to get to the "mass storage" mode?
Do you get the error when you click on "clear user data"?
The more specific you are, the better chance to find out where you're going wrong.
Start with a known good, properly formatted SD card. Be sure you are inserting the SD card properly as far as it will go. As you are pushing it in, you should begin to feel some spring tension pushing back against you, continue pushing the card in until you feel it lock into place with a definite click.
Check this video here:
Be sure your card is going in as far as that video shows and locking into place.
At this point put the batteries back in and..... before you turn the scanner on, connect it to your computer with Sentinel running. Now turn the scanner on.... does it go into the "mass storage" mode?
Can you now see and select the SD card in the "clear user data" function?