Hi tpf,
A couple questions:
1. Have you used the Sentinel software to update your master database? (You can make sure you have a recent update by navigating to "Manage Full Database">"Information" on your scanner)
2. Which system are you trying to monitor? Is it this one?
https://www.radioreference.com/apps/db/?sid=6906 (guessing based on your location). In other words, which online scanner feed are you comparing with?
3. Which antenna did you get?
4. As rkm suggested above, make sure you have the relevant services turned on by hitting Function -> Services and selecting "On". Quite a common problem! If you're unsure, just turn them all "on".
5. Are you hearing absolutely nothing on the system(s) you are interested in, or is it just lower traffic than you were thinking?
Honestly, I wouldn't go chasing different software programs until you have been able to troubleshoot through other potential issues first