@FlorinHiT When the router is in access point mode, it is set in bridge mode. And I guesss the "connected clients" is based on the DHCP server leased addessses. And when you have another device handling DHCP, you will not se any connected clients in the device set as "access point"-mode.

@MartinBer 

Thanks for the reply

But why when I make the settings from the beginning (after Factory default restore or Hard reset from reset button ) it shows me all connected clients, including wired clients?

Then if I reboot or the first power failure, it shows me 0 connected clients.

Strange!!!!

@FlorinHiT I tested my TP-link in accesspoint mode. And I can se wired and wireless clients. So my guess seems to be incorrect. You should probably be able to see the connected clients.

I tested this with a TP-Link Archer AX50.

@MartinBer Please simulate a voltage drop or reboot and then check if it shows connected customers..

@Kevin_Z Same happens to me, it's usually a hit or miss, sometimes some clients are shown, sometimes none, sometimes all (this is quite rare). It doesn't matter if they are wired or wireless.

Another related but different issue, when using Tether app it would throw a "waiting time exceeded" message or something like error retrieving information. When these messages are shown, the app displays 0 clients. However, some appear in the web admin page (again, not all).

Other than that, C6 works quite good so far and makes a good access point for the price.

@Kevin_Z Thanks, absolutely, being setup as AP mode I didn't even expect to see the client list (at least not the wired ones).

I have max 11 devices, the only WiFi AP is the Archer. I think I've figured out almost everything:

• The OP says that the 0 clients in web UI happens after a reboot, indeed, I've observed the list takes a bit of time to build after reboot, minutes usually, but eventually populates in my case. Workaround: patience.
• Missing devices are always the same for me: a D-Link 932L rev A camera (in 2.4GHz), the wired iSmartAlarm cube and an old wired ZOT print server. This gets interesting.

The camera might be listed after rebooting the camera, but not always. It's weird because it has to authenticate to the AP for the wireless link, so the AP has to know about it. Anyway, yesterday I replaced it for a 942L wired one and that's always listed (it's not even plugged to the AP but to the main router) so apologies for not providing more data about the old 932L one.

The wired ZOT print server is missing from the main router's list because it doesn't use DHCP. Mmmh, I've just printed something (I don't use it much) and now it appears in the AP list, but not before. Alright, now it makes sense, that ZOT device will only send ARP packets when a print service is requested, otherwise it's completely silent in the network, no broadcast, no anything. It's cool the Archer can detect it and not the main router!

Now comes the funny part, the iSmartAlarm cube. It's wired and connected to the AP, main router lists it because it uses DHCP. AP client list won't show it (showed it once time ago but never again). Since I was not 100% sure that the IP I saw in the main router belonged to the cube, I opened a browser with that IP (it has no management web UI so I got an error as expected). But... right after trying to get to the IP, the device shows in the AP client list!!

That's interesting, because the iSmartAlarm is not "silent" in the network as the ZOT server, in fact it's always "calling home" and logging all the actions in the iSmartAlarm servers. Somehow the Archer missed something that was triggered when I tried to access the iSmartAlarm device's IP (which you never do because all the communication to the device is done through their servers, not locally). Maybe that's related to the camera issue, you don't access the camera locally but through the server. But in the case of a wireless device like the camera, it should know it is connected because it is managing the wirless connection.

OK, now all my devices are showing in the list, but I guess the iSmartAlarm will dissapear eventually or after next reboot as whatever local communication is needed for the Archer to catch it is not something usual.

@Kevin_Z An update, yesterday I had a power outage, so of course every device rebooted. Everything works, but the client list (both in the app and the web) has been showing 0 clients since the outage. Just like happens to the OP.

This time, not even my "workaround" of pinging devices or enabling/disabling WiFi will work. Not even rebooting the router or waiting. 

It's a weird bug actually.

@mocelet Considering the time since reporting the bug to this day, I think there is no chance for an update of this bug. However it is an old model, it is at least two years old. 

I gave up the idea of ​​waiting forever for a bug fix and I focused on buying another device, another company.