I'm very new to my Deco m9 plus v2 system(set it up last weekend).  Thank you to the posters about the beta firmware.  I have been reading this forum for the last week.  I downloaded it and followed the instructions today to install.  The install was successful on all 3 units.  The app shows I'm now on 1.40 Build 20200319 Rel. 55255.  I can now see which node my computers are connected to in the app, but I can not login to the web interface.

I tried different computers, devices, and browsers.  I also restarted the nodes.  tplinkwifi.net brings up an error page saying "Trying to configure the router?" and putting in the direct ip address of the master node brings up a "This page isnt working" error.  This occurs on all devices and browers.  Did I miss a step or a setting somewhere that will enable the web ui? Any help for a newbie to tp-link products would be appreciated.  Thanks!

@vafan97 

put your main deco device ip 192.168.X.X:30000

DaveEdi wrote

Third Deco now upgraded. :)

@DaveEdi 

I encounter the same issue as you reported: 2 of my Deco's are updated nut the third one gives an error: 

Exception in Tkinter callback
Traceback (most recent call last):
  File "lib-tk\Tkinter.py", line 1541, in __call__
  File "upgrade.py", line 327, in upgrade
  File "upgrade.py", line 263, in upgrade_firmware
  File "upgrade.py", line 248, in call_tmpcli
  File "tmpv2\application.py", line 35, in request
  File "tmpv2\proto\tmp\client.py", line 195, in request
  File "tmpv2\proto\tmp\transaction.py", line 109, in sendrecv
  File "tmpv2\proto\tmp\client.py", line 144, in recv
BusinessError: Received packet with business error 9
 

How did you solve it? Any tips?

@Robert_M 

I just tried after a day or so. 

Just upgraded again using the non-beta firmware. 

Dave