There are a few threads regarding the client list, some are even few years old, but wanted to summarize the unsolved issue.

The problem some users face, including myself recently, is that the list of connected clients is empty (when set as Access Point) or just displays one client (the one being used to configure the device, when set as Router Mode). In my case DHCP is handled by another router (let's call it the main router). In fact, most issues refer to using the Archer as a second router or access point.

It looks like Archers build the client list by inspecting ARP packets, that's great for building a network map, but the implementation is not reliable, especially for wireless clients. Somehow they may miss them and pinging a device would make it appear in the list because the Archer catches the ARP packet. For a wireless device that has to authenticate against the Archer, the Archer should count it without having to catch any packet, after all it is managing the wireless link. When the list is empty, I've found no way to populate it, not even rebooting, unplugging from the mains, changing settings, changing mode, pinging, etc. In Router Mode it would show just one device, the one used to configure the Archer.

It's interesting to note that:

• In Router Mode there's a section listing the Wireless Stations. That list is perfect, it shows the clients that are authenticated in the AP and even the traffic. That's what you would expect to see in the wireless client list and in the Tether App. But, instead, you may get an empty or partial list, even when the Wireless Stations section is showing the correct information. So, the Archer knows it has N clients connected, but the method used to count them says 0 or 1.
• In Access Point Mode there's no Wireless Stations section, which is a real pity because then you can't look at the actual connected clients anywhere. And the wireless client list, both in the web and Tether App, would say 0 clients. It's weird that not even the device being used to configure the router is counted as a connected device.

The usual workaround to see the connected clients is watching the DHCP list in the main router, but of course that's not what you're looking for (that's just for DHCP devices and won't tell you the type of connection or the band). It's not a list you can trust to know the connected clients because someone might be authenticated in the wireless network but using a manually set IP.

I hope that you fix it eventually, it's been working for me until a power outage, then no matter what I do the list is empty and won't populate. Same as many users before using different Archer devices and different firmware versions. Difference being is that before you would ping a device and it would appear, not anymore in my case.