The "green" Sentinel is only for the 436HP, 536H_. SDS100, and SDS200 scanners.
You need the "red" version of Sentinel, which Jim linked above:
That's why you are seeing the 'all X's ESN'; the 'green' version of Sentinel does not recognize the scanner.
The correct version will recognize your HP-2, as well as capture the actual, correct, ESN.
You can export any Favorites lists you created in the 'green' software into *.hpe files, which than then be imported into the correct ('red') version.