Or maybe I need to use a wired connection (rather than wireless connection) when connecting my packet inspection computer to the router. I'm guessing it may have something to do with the fact that my router is using WPA2 encryption, instead of being unencrypted (like an 'open' wireless network). An yes, I'm using the latest NPCap driver installed by the Wireshark installer. The will result in a short Wizard that will install the package on your USB flash device and result in a new menu item being added to the main Portable Apps menu.

And this is despite the fact that I put a tick in the check box for promiscuous mode, for my wi-fi adapter in the Wireshark adapters settings, and made sure to select that adapter as my capture adapter. To install the package, choose the 'Options/Install New App' option from the main Portable Apps menu and select the file 'wireshark-.paf.exe'.

I can't see any communications between the router and another computer (at the ethernet packet level) or between any 2 other computers on my network (at the IP address level). At the IP address level, I can only see packets with my computer's IP address as either the destination or source address. At the ethernet packet level, I can only see packets between my router and my computer.

Wireshark https external device