@cheemcheem I have an Archer C5400 and the 2.4 GHz network keeps disappearing as well. It seems to be a broad issue.TP Liink support told me to set the Encryption to TKIP on the networks in advances > wireless > wireless settings. I did this today and am going to monitor it to see if the issue is resolved. 

@pschatzow Hey thanks for your response!

I don't think switching to an insecure encryption method is the way forward however, and you probably shoudn't use TKIP for anything other than debugging if you can avoid it.

See this wikipedia page for more information, particularly the part about NOMORE: "The attack against WPA-TKIP can be completed within an hour, and allows an attacker to decrypt and inject arbitrary packets".

Cheers

@cheemcheem 

I'm thinking something may have screwed up during the config reset. Manually upload the latest firmware on the router to see if reflashing the firmware undos any potential software issue.

@Tony Hi Tony thanks for your response.

I've manually uploaded the latest firmware and it hasn't fixed my issues.

It seems that my 2.4GHz network is not even up anymore with Smart Connect enabled!

@cheemcheem 

2.4Ghz might have died or the antenna. I would get a hold of our support at this point.

Live Chat: link
Phone: link
E-mail: link

@cheemcheem 

I have the same issue, in the past week my 2.4 keeps dying.  I have been debugging this with various configuration settings and also believe it is the smart connect.  Any new resolutions?  Or did Tplink just send a new one?  I've been using mine about 1.5yrs, wonder if it's still under warranty.  But my last $20 router lasted me over a decade so hope this $200 one isn't dead after a year and a half  :P

Does Smart Connect enables MU-MIMO?

@dreamdreamfruit Hey I got in touch with support a few months ago, and after talking to someone who was not very helpful, they put me through to the engineers and they were really helpful. 

Eventually after some back and forth with logs from my router, the firmware they sent has been running perfectly for the past almost 3 months now! 
 

The firmware I've been running is https://static.tp-link.com/2020/202003/20200318/ax6000v1_us-up-ver1-0-8-P9[20200318-rel14152]_beta_2020-03-18_16.03.53.zip. I'm not sure if it compatible with your router/region so use at your own risk!

I asked a couple of weeks ago if they would be releasing a non-beta/stable version of it (not that I have experienced any issues) and they said they will try to push the R&D engineer to release a new official version as soon as possible. 

@RaverCWB 

Yes MUMIMO is on.

@cheemcheem 

That's so interesting, thanks so much!  Yeah I called them and spoke to a guy for 1:15hr.  He had me try things like fixing the channel width and channel, but it didnt help.  My 2.4 goes in and out and is still going in and out.

They said the engineers will call me, so I guess I will let them do that before using the random firmware, but definitely appreciate your suggestion!!  Maybe I'll try it as a last resort.  Glad your system was fixed!!

This forum is really useful btw.  I wasn't really expecting a useful response, since most forum don't help much.  But this was truly useful, thanks so much!!!