@OCRibeye 

Please download and upload the following firmware if you continue to notice Deco units have a red LED light: link

The above new firmware could be updated through http://tplinkdeco.net, and there is an upgrading instruction in the zip file.

@Tony, thank you for the response.

It's been nearly a week, but I think I resolved the problem by manually re-installing the 1.5.1 firmware via a wired (ethernet) connection. Since that time, I have not experienced any further random disconnects.

If those issues resurface, I will try the firmware you linked me to.

Thanks!

Edit: I spoke too soon. Shortly after I responded to your post, I lost wifi connectivity again, and I noticed one of the Deco units turned red, although it returned to green a minute later. Because of how quickly the light turned back to green, I did not have a chance to check the other two Decos, which were on a different floor.

While my laptop reconnected to wifi immediately, my iOS device (iPhone 12) would not reconnect for 20-30 minutes. In both cases, I did not reboot the Deco units.

Per your instructions, I installed firmware 1.5.1 Build 20210520 Rel. 40426. I did so using the Update Tool, and I made sure my laptop was plugged into the main Deco with an ethernet cable.

I will report back if this problem persists.

@Tony,

After installing the firmware on June 18, 2021, internet was stable for a week. However, we lost internet connectivity three separate times on June 25-26, 2021. 

As before, our devices would show we were connected to wifi, but we had no internet connectivity. If I tried disabling, and then re-enabling, wifi, it would no longer connect to the wifi network. Only fix would be to reboot all three Decos.

@OCRibeye 

For Cox a good Chennel power level is anything between -12 and 12.  As long as you are in that range you should be good.   SNR should be between 30-50.  One thing I would suggest checking since the WiFi is still there but internet is lost is the modem logs.  I would look for T3 or T4 timeout.  These indcate a line issue and will typically need a maintenance tech to plant to resolve.  These are items typcially not looked at by Cox support.  They typcially only run a connection test to see if service is reaching your node.  They don't show the line quality.  

That is where i would look at next.  

@Carl 

Thank you for the reply. I checked the power levels (between +2.9 and +7.8) and SNR (between 43.1 and 46.0)

As for the modem logs, I do see one T3 timeout, although I see a number of these errors.

* SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

* SYNC Timing Synchronization failure - Failed to acquire FEC framing

Also, for the "Time" column, it is showing "Time Not Established."

As for your other comment about a line issue, Cox replaced the line from the street to our house within the last year. However, I will give them a call to see if they look into this further.

@OCRibeye 

Ussually the line issues are at the plant, where the CTMS cards are located it ussally isn't the phyiscal line but rather hardware connected to the line on their end.  1 T3 shouldn't be an issue but if you are seeing errors and Synchronization faliures it might be good to have them check.  If you get a level 2 or 3 tech ask for an intrusive line test.  If you do just make sure you aren't doing anything online at the time as your connection will drop during this test. 

@Carl 

Thank you for the response and explanation. I will monitor the modem logs in the next few days, and will call Cox to have them run the tests you suggested.

@Carl

Modem logs have looked totally normal (no T3 or T4 errors), yet the Deco went down three days in a row (twice today). I also tried rebooting the cable modem, and I switched the Decos around, so that one of the satellites is now the main router, but I lost internet connectivity again a few hours later.

I also sent an e-mail to support@tp-link.com, and received a response from a senior engineer named Parker Hu, who offered to troubleshoot the issue, although he asked I download an application called awesun. Trying to connect with Mr. Hu to see if we can remotely resolve this issue, or at least figure out what the problem is.

@OCRibeye 

Hello. Yes Parker is one of our senior system engineers and very knowledgeable.  If anyone can figure this out it will be him.  He is however in China so working with him would be after hours for us.  His day starts around 5-530 pm Pacific.  If you need help getting a session sceduled send me a private message with your contact infromation and what day and time works for you.  we would need at least a 1 hour window to call.  

@Carl 

Thank you for the response - Parker and I connected last night, and he used a remote connection to run some diagnostics on the router, but he could not figure out why I continue to intermittently lose my wifi connection, as he confirmed I had a good signal.

He believes it may be a hardware issue, and he sent me instructions on how to RMA. Unfortunately, I am unable to register my product, as the TP-Link website does not recognize the serial numbers printed on the bottom of the Decos, or the serial number printed on the box. I have submitted photos of both serial numbers to TP-Link Support, along with the proof of purchase, and hope to get resolution of this issue soon.