You mean when you disable NAT boost you can't login anymore?
When this problem happened, did your device connected to the router get IP addresses correctly？
Could you ping the gateway?

Strange. I don't have this issue on my C9.
Better try to clear the browsing history or change a browser to login.
BTW, what about the led lights of the router? Are they performing normally as expected?

Hi I have latest v3 Euro firmware, it is cloud version and I can reset password reset
Tplink tether says there are no clients connected- there are and wired and wireless clients, pppoe call to internet up.

iPad can't log in
Pc on chrome,edge or internet explorer can't log in
Laptop on same above browsers can't log in even after clearing cookies.

Net result:- can not log in on any device, change password option and still can't login.

If NAT Boost on cloud edition off causes no login, it's a non starter as I need to use QOS and bandwidth monitoring.

Resetting router to factory defaults I can recreate fault by simply selecting nat boost off and from there on router refusing to log me in and no prompts on screen.

Unless there is an easy fix I will have to box up router and return, a shame as the interface looks easy to interact with

Ok the issue is a bug caused by cloud option
Cloud option blocks local login and tether app data doesn't show correctly
Cloud option allegedly resets password-it doesn't

lights as you expect
Disconnecting wan causes cloud to disconnect-password hasn't been changed and can login.

reset router and ignored cloud sign up/sign in
can now login and use QOS etc.

Bottom line cloud login blocks any other login, tplink cloud only seems to support cameras and tether app waste of time

Having decided
1) a router online that will not login is a waste of time.
2)had a tp-link forum account for ages- whats all this moderation nonsense now
3) life is too short to be a beta tester and pay for privilege.

So I fully intend to return to retailer as not of satisfactory quality or fit for purpose.

Disappointed and decided to vote with my wallet and buy another brand

Actually, once you have created and login with a cloud account, then you will be able to login again only with cloud accounts, both on web management page or on Tether.
You can find more info about cloud management via the FAQ links:
[1371] What can I do if I forget the password of my cloud account bound to the TP-Link wireless router?(New Logo)
[1370] What are the differences between Admin & User cloud accounts on TP-Link wireless router?
[1366] How to register a TP-Link cloud account for my TP-Link wireless router to manage it remotely? (New Logo)

As for the bug, could you provide more clear and complete descriptions in short sentences? For example, sign in a cloud account, turn off NAT boost, etc. And I'll make a test on it.
If it's a bug, we will fix it in the next firmware release.
Thanks.

This is exactly why it will be returned for a refund.
Yes I know you can only login once cloud enabled, the tp-link cloud app accepts user name and password and logs in- but data is incorrect and corrupted.

The cloud user name and password will not allow browser based login from any device while the wan is active and the internet is online.

Pull the wan Ethernet and Internet pppoe becomes offline-surprise surprise- you can login.

Anyway I've had enough of the moderation of posts-being treated like an idiot.
Failure to comprehend that the v3 EU firmware is bug ridden.

It's going back and I intend to use openwrt, ddwrt or even pfsense and untangled.

The hardware suits my application, the firmware is garbage and appears impossible at this time to downgrade via tftp recovery and C9 V3 DDWRT install needs warranty voiding physical connection to it.

I've learnt from bitter experience that bug ridden technical products it is best to return asap as support promises are generally vapourware-sorry but it is going back for a refund as basic features such as being able to login and work as expected are a must.