@Kevin_Z 

I have the same problem with the Archer AX11000

i did all the items that are quote NG!

they claim high speed in their web site with pictures like a rocket but its a dud.

@Kevin_Z 

Have the same issue myself on Fios Gigabit,, don't have the model of the Verizon issued router but connecting my PC straight to my ont I get over 1000 up and over 1000 down, connecting through my ax6000 gets me over 900 down but only 150 up (if I'm lucky) I have tried everything mentioned above with no resolve,,, getting ready to throw this in the bin and pull the trigger on an Asus

@Kevin_Z 

I will check for software but I believe I have already disabled most of the software from asus and have already changed my power settings and have my lan set to 2.5gbps full duplex, however this is not isolated to my PC,, every device connected through the ax6000 is suffering from slow upload speeds, I am going to install an eero 6 tonight and hope I'm done with it

@Kevin_Z 

-ISP TDS.net

-ISP router T2200H 

-Rated Speed Down-1000Mbps UP-400Mbps

-Internet -> T2200H - Down 998Mbps - 401Mbps

-Internet -> AX6000 - Down 930Mbps - Up 1-2 Mbps ->with any VPN, Nord, PIA, IPVanish <-tested

-Internet -> AX6000 - Down 930Mbps - Up 350Mbps ->with no VPN

-Internet -> T2200H  DHCP on -> AX6000 DHCP off as access point - Down 950Mbps - Up 400Mbps  With or without VPN.

-Internet -> T2200H  DHCP off -> AX6000 DHCP on as access point - Down 930Mbps - 1-2Mbps -> With or without VPN.

Internet port negotiation was set to 1000 full, and tested on auto and 100. 

Also, when hooking up a second computer while the first is hooked to VPN getting slow speeds, the second, not on VPN, will get relatively full speed.  It is not network-wide except when AX6000 is the access point and the DHCP server.  

Used 2 different computers having only 1 device connected at a time: rebooted Router and restarted machine between each setting change. I was messing with QOS settings and momentarily got up to 20Mbps with VPN on only AX6000 when I reduced the upstream from 1000Mbps to 500Mbps; however, it did not stick after another reboot, and any other changes made no difference.

Last night As I was testing the AX6000, it did get stuck on 1Mbps upstream no matter what configuration I did. <- don't know what that was about, and I was going to throw the Router away at that point, but when I woke up, I pulled it out of the trash and began testing again, and after a factory reset, I did not have the same problem. 

Did all troubleshooting mentioned, plus more.  I have turned off all settings, no matter how irrelevant they may be, and then turned them one by one in every variation. 

The Router worked OK, never meeting the performance expected, from May 8th, when I bought it until I noticed a problem about three days ago. The firmware update was done the day it came out. 

Firmware Version: 1.2.4 Build 20210719 rel.12163(5553)  
 

Edit: I've noticed if there is any network traffic from more than 1 device all download speed is reduced to 1-4Mbps.  When network traffic stops and only one device is talking it goes back to full upload speed.  Big problem since I have NAS, Cameras, Plex server, Phones, TVs, all using traffic at the same time frequently. 

The router is on default settings directly connected to fiber except for the troubleshooting steps mention in OP. 

@Kevin_Z I have the same issue and the solutions provided here don't work.

In fact, I already sent my first AX6000 back to Amazon for repair. A week later I was told that the device can't be repaired and I was sent  a replacement device. The replacement device has exactly the same issue as the original device.

My internet service provider is Proximus (Belgium) and with a wired connection I get a decent upload and download speed (https://www.speedtest.net/result/d/365304417). However, when connected to AX6000, the upload speed drops to zero (both wired and wireless) and SpeedTest won't even finish.

Considering that AX6000 is the most expensive router I've ever had I'm at the end of my patience now. I have until 25 November 2021 to return the replacement device to Amazon and unless I will be provided a working solution before that date, I will return the router and ask my money back.

@Kevin_Z 
AX11000

-Firmware Version: LATEST 1.2.3 Build 20210719 rel.14861(5553)

-Hardware Version: 1.6

- Name of your ISP

Verizon FIOS

- Model of the ISP provided modem

I-211m-L (ONT)

- Download and Upload bandwidth provided by ISP

1Gbps U/\D

- Speedtest result when connecting to the ISP modem

900+mbps U/\D 940+mpbs

- Speedtest result when connecting to the TP-Link router with an Ethernet cable

900+mbps U/\D 270mbps