ArcherC8 wrote

Did you use the same SSID on the Linksys?   

yes

ArcherC8 wrote

By chance, are the two devices that will not connect 2.4 or 5 only ghz? 

All three thermostats will only connect to 2.4.  The SSID used by all three thermostats was the SSID for the 2.4 connection.

ArcherC8 wrote

 Try deleting/forget the network settings on the two devices and then reestablish them.

I tried that several times.  It did not resolve the problem.

The next thing I would try is moving the router, turning the router, move the antennas if moveable, changing the height of the router, use different WIFI settings such as a specific channel instead of AUTO,... If you can establish a connection then you know it has to do with the WIFI signal being blocked or interfered. A longshot, does your thermostats have firmware that may be needed to updated?

ArcherC8 wrote

The next thing I would try is moving the router, turning the router, move the antennas if moveable, changing the height of the router, use different WIFI settings such as a specific channel instead of AUTO,... If you can establish a connection then you know it has to do with the WIFI signal being blocked or interfered. A longshot, does your thermostats have firmware that may be needed to updated?

Because the thermostats connect to the guest network without changing the router position or any settings I don't see how router position, etc, is the issue.

Unfortunately there is no firmware update for the thermostats--but why would it be needed if the thermostats wil connect to the guest network with wireless security activated?

ArcherC8 wrote

good point... Could the coverage pattern be different for the guest network? I do not know for sure but would think the guest WIFI would use a different channel than the main WIFI. So I would explore different WIFI settings.

Interestingly, there is no option to either view or change the channel in the guest network.  In the regular network the current channel is displayed when auto is selected and there is the option to specify the channel.

Kevin_Z wrote

@Bob999 

 

Thanks for your reply; cause you have the same issue on Archer AX6000 and Archer C5400X both, we can do further analysis and try to figure it out. 

I no longer have the C5400X--I returned it because it had other problems.

Kevin_Z wrote

@Bob999 

 

Except the three thermostate, do you have any other wireless devices? Do they have the same issue when connecting to the TP-link wireless network? 

 I have many other wireless devices, Roku, FireTV, Smart phone, Smart TV, Laptop, etc.  All connected to both devices without issue.

Kevin_Z wrote

@Bob999 

 

And what are the model numbers of the 3 thermostate? 

The Thermostat that connects is RTH8580WF.  The 2 Thermostats that don't connect are TH8320WF.

The AX6000 is V1, Firmware is:   1.0.6 Build 20190822 rel.26396(5553).

While I no longer have the C5400X I can sorta answer the question about hardware and firmware.  Hardware was V1.  For firmware it was first the latest stable version posted on the support site and then later it was a beta version posted by TPLINK in a thread on this site.,

I found the link for the beta firmware in the TP Link SOHO community in a thread labeled "C5400X - Internet Speed issue". 

Re:C5400X - Internet Speed issue

Hello Everyone  

 

 

We are happy to annouce a new Beta Frimware for this issue.  This Fimware addresses the speed issue while not affecting the status of your router's homecare features.  You can download the Firmware here:  http://support.tp-link.com/f/3ba5085b7c/?dl=1   Please let us know if it helps or if you have any issues what so ever. 

@Bob999 Thank you!!! This solution worked!!!