@Kevin_Z 

Thanks For you reply . I have bought this Router to use 5GHz Specially . If I think to use 2.4GHz then I was happy with my previous router WR841N . I was Planning to switch from 2.4GHz to 5GHz, that's why I bought this 5GHz Router . I bought this router at 22/05/2021, that means 12 Days ago . I am using the Qualcomm Atheros QCA61x4 PCI-E Wireless Card 1200Mbps to use 5GHz . If I use 5GHz - 3/4 hours at a row then It disconnect 1 or 2 times and Some Days It did not disconnect at all . When Wifi disconnects, at that time Internet LED remains green, after againg reconnecting wifi I was entered the router and I saw Status is showing connected to the Internet and IP is Showing also , no problem found there .

I have also connected to 2.4GHz and I found that router is only 144Mbps capable at 2.4GHz and 866Mbps capable at 5GHz . That means your router is 150 + 867 = 1000 Mbps Capable, not 1200 Mbps Capable  !! Just Look the Screenshots of 5GHz & 2.4GHz Below :

2.4GHz :

@R-O-N-Y 

Something may be wrong with your adapter.. for me 2.4 ghz shows 300 mbps only..  check with other mobile devices..

@Souvik30 

No Bro , Adapter is OK . I am using this Adapter for Few months . It is fully tested with my previous Router WR841N . The Problem is in Archer C6 V3.20 Router . You also have a router of C6 . So, Check your's Archer C6 2.4GHz in Windows 10 and you will also find that it 144 Mbps, not 300 Mbps . I am over sure in this point because I have Checked another C6 Router Which has the same 144 Mbps Capabilty .

@R-O-N-Y 

As you can see i am getting 300 mbps.. on both pc and phone . Try to change the channel width to 40mhz

@Souvik30 

Thanks dear . As I said before my Wireless Card is totally Proven through test with my previous router WR841N that it supports 300 Mbps by default. But C6 is showing only 144 Mbps !! According to your suggestion - I changed the Channel Width at 40MHz and wow !!! now Link speed is showing 300 Mbps . But in "Auto" mode it is just 144 . My previous router was 300 Mbps without any configuration changed . Again thanks dear for your suggestion . At last I could know that my router supports 300 Mbps at 40 MHz . :)

Here is the 300 Mbps Screenshots @ 40 MHz Below :

@R-O-N-Y 

That's great.. Also scan for wifi clients in your area with wifi analyser app on your phone.. if your area is crowded with many wifi then tp link will automatically switch to 20Mhz to avoid interference with other wifi..

@Kevin_Z  and Souvik30 

Hello Dear,

Today I was surfing Internet For 3 Hours . In this 3 hours router's Performance List :-

1) After using 2 Hours - First Disconnect of 5GHz Wifi . Then I Checked the LED Lights of Router . There only 3 Led lights were glowing but the 4th Internet Led light was totally Off !!! Then I connect the 5GHz Wifi again, Wifi Connected but showing No Internet . Then I Login to router - In Status Display was showing "Poor Network" and IP was showing . After that I switched Off the Power Line of Router and Power up again - then Router started and all of 4 Led lights glown and Internet came back .... !! and Next -

2) Internet came back and started surf again - After 1 Hour surfing - again the Wifi Disconnected, then I checked the Led lights - this time 3 Led lights were Green and the 4th Internet Led Light was Red . Again I Login to router and found same message "Poor Internet" and IP was showing . Then I switched Off the router and switched on and 4 Leds came back as green and Internet came back ... !!!

This is the history of using 3 Hours of this router ... !!! Don't blame my ISP Please  becasue I have been using this ISP past two years with my previous router WR841N . And I had not found any issue like this with my previous router WR841N . My ISP and WR841N is totally proven . And I am facing this problem after buying this Archer C6 V3.20 from 15/16 Days . And I have bought this router 15/16 Days ago . So, the problem is definitely in your Archer C6 V3.20 .

If you google the reviews of this Archer C6 V3.20 router, you will find a lot of the same issue like as mine . This problem is not only mine , It is the problem of a lot of people .

@Kevin_Z  I am requsting you to tell your technical team about this problem and update the Firmware Immediately by solving this problem . Otherwise take back the router from Me and from whole Market ... !!! Because this router is not worth of TP-Link Brand - It has really serious stabilty Issue . I am really disapointg with this TP-Link router's service . My money may be  totally wasted ..... !!!

@R-O-N-Y strange.. i never faced this issue..  try to order a replacement if it's still in replacement policy.. something is definitely wrong with the router.