From page 26 of the User Manual. I was having the same trouble until I found this yesterday.
How to Install Sentinel Software
If you have not already installed Sentinel software, follow these procedures.
1. Use the USB cable to connect HomePatrol‐II to your PC.
2. Turn on HomePatrol‐II if it is not already on. Select Mass Storage. The HomePatrol‐II screen
turns white while it is connected to the PC.
3. Sentinel software installation should begin immediately. If it does not, open the drive folder and
run Setup.exe in the Setup folder.
4. When installation is complete, Sentinel software and various documents are installed on your
PC.
5. Disconnect the USB cable. HomePatrol‐II begins initial setup procedures.