Hello -- sincerest thanks for reply and suggstions.

I would like to add the ff. that did not appear in my original post:

 

1 - when I connect using WIRED (Ethernet Cat6 cable)  everything runs top speed (my ISP subscription is 100 mbps fiber)

2 -  whether the WiFi client is a laptop ot a smart phone or tablet, the WiFi connection is very slow, weak and easily dropped.

3 - The Archer A20 has the option to set the radio signal at low,medium,and high.  I have always set it at high, and it really performed well

     from Oct 20, 2020 until yesterday, Jan 9, 2021.

4 - When I reported my first post, I had already disabled the 2 newly created Guest WiFi networks, no difference.

5 - Yes, I also tried the Isolate AP mode and it didn't make any difference.

 

My additional question is:

 

Q1 - are there diagnostic tests solely to check the hardware of the TP LINK C4000 A20?  Specifically to check

if those bands are trasnmitting at a signal level they're suppposed to be?

 

I am somewhat inclined to say -- at this juncture -- that it is the hardware that is defective -- which leads me to another question: 

 

Q2 - Does TPLINK have any 1 year warranty on this product?  I purchased it from Amazon.com and had it shipped to a foreign country

(Philippines) where I am now, and had it installed.

 

Your advice and guidance is highly appreciated.  I hope you can suggest the next step(s).  I am desperate to get this working again,

as this is for a small family business that is highly dependent on WiFi.

 

Thanking you for your attention and kind consideration.

 

Sincerely,

R. Tan

 

Thanks for response -- yes, I am very sure that was my only change, adding guest networks.

 

I tried something in the interim:  I recycled power on the ISP's modem (never did this before).

When everything came back, I tried to connect to the WiFi -- the first time, I got a message from my

Android cell phone that says:  access to WiFi rejected/denied. 

I note that the password was the same, i.e., had not changed.

 

I tried a second time, I stood closer to the WiFi router and this time, it connected after a "struggle".

i.e., the "access rejected/denied" message didn't come up.

 

Then I checked the signal strength (a common feature on Android cell phones).

As with all my previous tests and retries since this problem started, it showed a wiFi strength of Poor,

and a link speed of just 2 mbps.  I was as close to the WiFi router as can be.

 

In the normal working days when I did not have this problem, I had always a number of 70 mbps and

sometimes even higher -- and be at a far distance.

 

Are there diagnostic tests that can be run to check the radio signal coming out of the A20?

 

Thanks again for your paitence and kind consideration, I find this experience rather weird and am

at a complete loss as to how something can suddenly misbehave overnight.

 

Any further tips and guidance will be highly appreciated.

 

Sincerely,

R. Tan

 

 

Hello Mr Ivaylo,

 

Per your instructions, I performed the steps accordingly and attach 5 relevant screenshots:

 

- the first 2 are Internet Speed Tests from within the TPLINK A20 in ADMIN Login mode.

  I accessed the A20 router by connecting an Ethernet cable (Cat6) into one of its LAN ports and typed the IP address to get in.

- the next 3 screenshots are the WiFi settings of each of the 3 bands.

- Smart Connect was turned OFF.

- Guest network was OFF.

I rebooted the A20, waited about 3 minutes each time I rebooted, then logged in using a smartphone most of the time.

I also tested using a Win10 laptop using WiFi.

 

My findings/ experiences:

 

(1)  I am now able to Login successfully from my Android cell phone and my Win10 laptop with WiFi.

(2)  Once connected, the signal strength (as reported by the WiFi icon/symbol with 4 arcs) was 3 to 4 arcs: good to excellent.  

       This is the experience for both cell phone and laptop.

(3)  However, after successful Login, within 2 to 3 minutes of accessing the Internet (while all worked well), the connection is lost.

       "No Internet access" is always the message I would get back on my cell phone or laptop.

      I also note that discovery by the cell phone or from the Win10 laptop always took at least 2 to 3 tries before the SSID could be found.

      And I was always physically within 4 to 5 feet of the A20.

(4)  All WIRED connections which go through a Cisco SG-300 switch (connected to one of the LAN ports of the A20) work perfectly.

       Every device that is connected WIRED has no problems with speed and performance.

       Only the WiFi connections are not working in a reliable manner.

 

I have performed these tests repetitively to ensure that I was experiencing the same results consecutively, i.e., not just a "one-time" experience.

I must be missing some fundamental setting or configuration detail.  Hope the above can help to pinpoint what I am doing wrong.

I note that this A20 ran perfectly well (with Smart Connect turned ON all the time) from Oct-20 to around Jan-08, and then suddenly one day

all WiFi connections were dropping off the A20.

 

Thanking you for your attention and kind consideration.

Sincerely,

R.Tan

 

 

Much thanks.  I've used 2 to 3 WiFi monitors and the A20 signals were the best of all -- typically in -40 to-60 dBMs.

I just do not understand why it cannot connect to ANY device, or if connected, drops within a minute or 2.

I've spent all of the last 2 weeks trying every permutation, and give up -- any suggestions?

I know the hardware of the A20 may be in question, but everything else is working -- 2 other A7's are connected to it as independent WiFi networks (i.e., non-AP mode)

and those 2 are working fine.

I've ordered a new TPLINK which I plan to connect to the A20 as AP (to simplify my life as IT support).

Thanks for all the help and your patience.

Best,

 

 

Thanks, will do -- I already tried a soft reset by restoring to factory defaults and reconfiguring everything, and that didn't work. Is there a genuine difference between the HARD reset to factory defaults versus a SOFT reset to factory defaults? Thanks for your inputs and patience, much appreciated.