@alien-link I have a similar, though slightly different, issue on my new Archer C2300, firmware 2.0.3 Build 20180611 Rel. 77668.  Not only do some wireless clients not show up in the Wireless Clients list, but some show up in the WIRED clients list.  I'm using the router in Router mode.

@alien-link 

same problem with AC750 travel router in AP mode. Spent hours yesterday trying to figure out why devices wouldn't connect. Eventually figured out they were connecting but not showing in the client list. This is not a feature it's a bug that needs fixing. 

@alien-link Same issue on the VR2100,  UK version,  new device just purchased, very dissapointed.

@Carl 

Same issue on my AX1500 wifi6 router

@Carl 

Hi Carl. Any update on this? Its been almost 8 months since the issue was reported.

@alien-link Mine is doing the same thing. I just put a AX-11000 wifi 6 2 days ago. It is in access point mode and my upstream router is doing the DHCP. I can see some devices but their all unknown and I can't identify the mac addresses that aew shown to any device. No ip address is showing. I can see the devices in the upstream router but of course they show as hardwired because the ax11000 is connected via ethernet to the router port. What is going on with this. Looks like my now a fix could be implented.

@CraigSchafer Same here on the ax11000 just installed 2 days ago. What the heck you know with something that cost this much. 

@dfb8085 

Yes, the truly sad part is that in one of the post, a person from tp-link claimed that this was acceptable behavior for a WiFi AP to not properly show the list of connected wifi clients.  So even though the AP for authentication purposes is tracking connected wifi clients, this internal list is not show to us on the web page.  Instead, someone decided to put up an ARP list of clients (unrelated to WiFi connections) under the false assumption that this was a good idea.  And to this day, they have not fixed this major bug and security flaw...  Really sad behavior for an otherwise good company.

@Carl  I hate to break it to you, but any client that is configured for DHCP MUST send an ARP broadcast when the IP stack initializes (FF:FF:FF:FF:FF:FF) which is heard by all devices on the same layer 2 network (wired and/or wireless). That's how a client announces its "request" for a DHCP address.

There are 4 steps in the DHCP address assignment (an easy acronym to remember is ROSA). 
 

Request - ARP Broadcast by the client

Offer - directed to the MAC address of the client initiating the request 

Selection - the client sends a response to the DHCP server to tell it that it will/won't accept the address

Acknowledge - the DHCP server acknowledges the selection and marks the address as being leased

If any devices are not following this, then quite simply they aren't RFC compliant and it would be amazing that they even get an IP address at all!

Step 1 is always heard by ALL devices. If any devices aren't hearing it, it would likely be a firewall policy blocking the DHCP request, or defective code. 

I've never had to change what I'm using as my DHCP server in order to get a wireless device working on the network. 
 

And, if a wireless client is associated to an SSID on the WiFi access point, that association is done entirely at layer 2 so the AP knows the MAC address of the client. 

This TP Link device sounds like it's in desperate need of a factory recall. I just told my friend to return his. 

@alien-link Thanks for the informtiom. A lot of people with various models of TP link routers are having and been having this issue for the past several months. Tp Link is aware of the problem but can't seem to issue a fix from what i have read. 

I have about 3 or 4 devices that I did a DHCP reservation so that they would have a certain IP. The TPLink router is operating in AP mode and the upstream modem/router is handling the DHCP duties. I have one device that did not pick up the DHCP reserved IP and is still operating on its old IP. I see it in the orginial modem/router as active but when I look in the TPlink router it is not there and neither of course is the DHCP reserved IP. Two of the items show in the router I can idenitfy them via their MAC address. The rest of the wifi devices don't how at all in the TPlink but do in the original /modem/router. All this cumberson makes it hard to manage anything.