I have a clarification to make on my last post and a comment to make on the pic in post #11.
Clarification: Activity Log is not in the same menu as LCN Finder. You may already know where to go to get to it, but I'll tell you anyway just in case. If you start out using the menu options ("Menu" in the lower left corner, then "Advanced", then "Advanced" again), you then go "Analyze System", then "Trunked System Analyzer" (directly above the "EDACS/LTR LCN Finder" line). From there, select the appropriate system and site, and after you do that, you are presented with the "Select Tool" menu. On the lower left of that list is "Activity Log". Click it and let it run for a while (anywhere from a few minutes to a half an hour should be more than enough).
Further to add: In order to get the files created by Activity Log, do the following (again, you might know this, but in case you don't, here it is): Plug your scanner into your PC and select Mass Storage mode. In Sentinel, under Tools is the Activity Log Viewer. Open it, then click the only icon (looks like an arrow coming out of the HP1's screen). Follow the prompts (select your scanner, choose/name a Collection (or let the program choose for you), etc), and in a bit you should have the file showing in the viewer window below said icon. Now, if you want to view it yourself, click on the collection name (same rules as Windows tree view applies, click on + to expand, click on titles to open said file, etc). But in order to send it to us in this forum, you have to go to where the actual file is stored on your hard disk. If you didn't make any changes to the default settings when you installed Sentinel, the activity logs will be in "My Documents\Uniden\HomePatrol\ActivityLog\" with folders for each Collection. If you zip up the .log file in the folder (even "Send to>Compressed folder" is fine), it will take up a lot less room than the raw .log file.
Now, for what I noticed about post #11 above. You mentioned that the LCN finder shows just a blank line on that one frequency. The way the LCN finder works is it has all squares grey at start, meaning any frequency could be any LCN. As it figures them out, it puts a white square in the column that corresponds to a given frequency's LCN value. All other squares in that row are turned black to indicate that the other columns are not going to be used for that frequency. The problem is, the HP1 thinks that the LCN is 4095 ... so the white square is WAY off the right side of the screen, far far beyond what you can see.
Not much help, I know. Maybe the data from Activity Log will shed some light.
Are other scanners able to monitor this system at all?