@thomasglee 

Remove the wireless profile or forget the network and connect to it again on your devices.

If you still have the issue get a hold of our home support: https://www.tp-link.com/us/support/contact-technical-support/#Hotline-Support

If the client device has the correct password but the Deco is saying otherwise something may be going on with the software in the Deco.

@thomasglee 

Someone else solved my problem, not being able to connect to Netflix.  I am guessing Apple TV is the same and it's not capable of connecting to a 5G network.  Go to more on the bottom of the App on your phone and then go to Guest Network, let it create one and turn off 5G.  Good luck.

@Tony This is similar to a new thread I just posted.  Except for my new Deco M9 Plus install, I created a brand new network SSID and a new password.  Then I connected all 19 devices to the new network.  Only 1 of my devices (so far!) has connection issues - a Macbook Air laptop. Very odd; the password is correct and it's inconsistent. Sometimes it joins the network, but most of the time it cannot.

I just bought M9 Plus and facing the same issue. Can anyone help? I tried resetting SSID multiple times, updated password to avoid any special characters, Removed and added new SSID but nothing is helping. On reading many threads it seems Firmware issue? Any update on how I can resolve this?

I tried with online agent but he had no idea of how to resolve it or look for firmware issue. He just asked me to make my other Deco unit as Main and stated it will solve the problem. Guess what it did not as it seems some issue with Firmware!!!

Please help.

@Abhi_2020 Did you try to reboot Deco M9 Plus from the app?