Had mine up and running for about 18 months with no problems.

I am having a very similar issue. My setup is

Hardware:   ArcherC5400 v2.0

Firmware:   1.2.2 Build 20170912 rel.56240(5553)

With increasig frequency (several times a day) the Internet connection will disappear. The wireless networks still show up on the clients, but no Internet access...

I would usually suspect my Internet provider's equipment or service, but during these "outages" I am unable to get to the TP-link router home page. A provider-level problem would cut out the Internet, but would not interfere with getting to the internal router interface.

The conenction comes back in a couple of minutes, usually.

This is BEYOND aggrevating, as these resets completely kill VOIP phone calls, gaming sessions, and (most importantly) work-related teleconferences.

I carefully reset all hardware connections, rebooted router hardware many times, but the problem is becoming more prevalent.

Had similar intermittent problems on C9 with 2.4 GHz clients dropping and having to be re-set completely. This is an issue not limited to TP Link... other mfgr forums have similar posts. If you can live without it, turn OFF the 5 GHz service. Problem solved for good.

@Pablos.Dog8one 

I've seen users report issues with the 5G where it would drop or they get hit with "Not supported in your region".

In your case it seems like you were talking to support already. If issues still happens, I'd follow up with support. If the antenna is faulty the device may need to be replaced.

Other things you can still try is to change the wireless channel and width to see if that helps with the dropping. For example, changing the 2.4GHz channel to 11, and the width to 40 MHz.

@Pablos.Dog8one 

I gave up and RMA my router after 2.4GHz started again cycling off and on. Hope the replacement lasts longer. I see this model is no longer in production. 

I have recently had the same problem approx six months following purchase where only the 2.4 network drops out for no apparent reason.

I dont know this has happened until i try to use a device, until I reboot the router it will not come back on.  In addition all the homecare items are disabled when i check the router status in Tether, which is also a little sluggish when these drop outs occur (using 5.1 network to log into iphone with Tether app).

So im not only concerned that the 2.4 network is dropping out without any apparent reason or notification but also is the firewall, anti virus and the likes actually active when this occurs.  I checked the system log which is full of the usual rubbish about the LED controller (6 pages a day of faults with the LED controller is a joke) but there is no entry for either the network dropping out or the Homecare issue i described.

I have done numerous resets and done all the things everyone else described in this post but with no luck, its just happened again today which is why i came here to see if there is an answer, but would appear not yet.....Be time for a new router by time TP-Link get round to sorting it me thinks ;o(

@CaptainHQ 

Most likely you have a faulty radio. If you still have warranty "2 years", then it can be replaced after going through the troubleshooting with TP-link.

TP-link replaced mine with the C5500X, as the C5500 is no longer in production.

The most reliable router I have had is the Archer C9 v2, still being used at another property. I just perchased a Acher C9 v5 for a back up.

@Pablos.Dog8one 

having identical same issue. wireless drops after a while and takes forever for everything to reconnect. 40+ wireless devices this is getting really frustrating.

either the HW is failing on everyone at the same time or theres some sort of software bug going on. Why cant we log in via SSH and enable more detailed logging or something?????????

@giento 

I got a replacement from Amazon (where i originally purchased it from) at the same time I identified the issues I had with TP-Link support.  I have to say the response i had from TP-Link was very negative, they didnt seem interested and eventually suggested replacing it anyway.  The replacement has had the same problem however has only occurred twice so far.  The system log is once again full of errors, that i do not understand and TP Link have also not answered from the logs I have sent them.  Perhaps they dont understand it either.  I think the  best way forward at this point is to continue with replacements and when the time comes to replace it for a new model, DO NOT buy TP Link again.

@CaptainHQ 

Was it replaced with the c5400x? 

That is what TP-link sent me and it hasnt had any issues thus far.