Could be a number of things, all fairly minor. . .
Is the USB cable properly connected at both the scanner and the computer?
Are you selecting Mass Storage by pressing the "E"? If you press "." for Serial Port, that could be the issue.
Do you have the ability to remove the SD card from the scanner and install it directly in your computer? Some computers have slots for SD cards, or you can get a separate SD card reader. You'll need an adapter card, but one probably came with the new card.
When you do this, that SD card will show up in your computer, using Windows Explorer, as a Removable Drive. Sentienl will still treat that Removable Drive as your scanner for programming the card purposes.
Last, just to confirm, when you first installed the new SD card, after formatting it with the SD Formatter utility, did you either go through the "Clear User Data" process to install the appropriate files on the new card?
As I understand it, having the ESN on the card isn't critical to scanning. That's something the scanner will do during the write process. So that means one could swap SD cards from one scanner to another scanner and things will still work.
