@Chadwick21 

Actually this was my fault i meant to follow up with you but i was waiting on more information.  The answer they gave did not give me a full answer. 

I want to make sure I have a grasp of the situation fully, to ensure i am explaining it correctly to my System Engineering team.  

If you connect to the WiFi generated by the router you are not able to connect to the router via Tether but when you connect to a free network you can?  is that correct?.  

If so, please provide a few more details so that we can give the engineers a clear picture.

1.  Who is your ISP?

2.  make and model of your Modem?

3.  Is you WAN/Internet IP on the C2300 a Public address or a private (Private IPs are 10.x.x.x. 172.16.x.x to 172.31.x.x, or 192.168.x.x)  

Thank you 

@Carl  I apologize for the late response. I have just realized that there was a second page to the forum post.

Yes that is correct, Ii I connect to the WiFi generated by the router I am not able to connect to the router via Tether but when I connect to a free network I can connect to the router via Tether.

1.  Who is your ISP? - Xfinity Comcast

2.  make and model of your Modem? - Zoom Model, Model 5345

3.  Is you WAN/Internet IP on the C2300 a Public address or a private (Private IPs are 10.x.x.x. 172.16.x.x to 172.31.x.x, or 192.168.x.x) - IP Address is 73.x.xx.xxx

Again I apologize for the delay.

Chad

@Chadwick21 

Chad,

Not a worry sir.  I have taken this  infromation and forwarded to my system engieering team.  And thank you for the clarification we orginally explained that local access worked buy remote access on a different network did not.  This changes things a bit now that we know local access is the issue.  I will update as soon as i have more information.

Best Regards 

@Carl Was there a resolution to this?  I'm having the exact same problem with my Archer C9.  I haven't been able to check if it connects via a free network, but it absolutely will not connect via the local network.

@hessiebell 

One thing to check is this:  

Please suggest customer to check the Administrator page.
There is a feature called "Unrestricted LAN Access" which should be enabled by default.

If it is disabled, only allowed device have ability to access the router neither on web or tether app local.

We are unable to access customer's router by any way so i suppose customer might changed this settings

With the Archer C9 only the V4 and V5 have the ablity to link to a TP-Link Cloud and allow the Tether app to connect to the router remotely from a seperate network.  

@Carl 

Hey gentlemen, do we have any working solution to this issue? I have exactly the same problem.. 

I´m using C2300 in AP mode and the Tether login always failes as it is described in this toppic. I tried factory default, 2 Android devices and it is still the same. My old AC1200 has absolutely no problem with same setting.

Thanks

@Carl I don't have a setting called "Unrestricted LAN Access".  Is it the same as "Access for All LAN Connected Devices"?

@hessiebell 

Yes i believe so.  Some routers do describe the setting differently 

@Chadwick21 Have you tried user name and password as 'admin' (without quotes)

Same issue, Archer C2300 v1.0, current firmware, just setup the router via web browser in AP mode. Connected to WLAN (non guest) and management enabled from all devices. Unable to login from Tether app with the same error message as OP. A solution posted here would be nice