@terziyski thank you. 
 

I went out and bought the below: 
 

TP-LINK 300M Wi-Fi Extender Booster & 600MBPS Powerline.

I am connecting my Xbox series X to the Wi-Fi extension adapter via Ethernet which is linked to the powerline adapter and the router (all by Ethernet)

Initially it seemed to work well, however I now seem to get NAT type errors on the Xbox and the connection doesn't seem to establish correctly. I am assuming it's a setting on my router and how it's talking with the adapters and Xbox, but any ideas? 

  @terziyski 

Thanks for this. It is a TP-LINK TL-WPA4220 with a powerline adapter N300. 

The TP-LINK TL-WPA4220 is upstairs connected via ethernet to the xbox. The TP-LINK TL-WPA4220 is connected to the Powerline adapter N300, which is connected via ethernet to my router. 

I am in the UK and using BT Fibre Broadband, the router/hub is the BT Smart Hub 2. 

I managed to use the set up for a short period and noticed much better gaming performance on the xbox, however now having issues! 

I also have a TL-WA850RE on the same network, however this provides wireless connection to another room - not sure if this may be causing issues? 

I am assuming the issues are IP address/settings related! 

Otherwise, a very simple network set up. Thanks in advance!

  @terziyski 

I have attached a screenshot from the app, not sure if this is what you need? Not sure why it is just as "undefined" though...? 

On the TL-WA850RE-EXT, DHCP settings were "on" which I have now "disabled" - what does this do, please? I am using it in Range Extender Mode at the moment (its in a spare bedroom, connected to the smart hub only via wireless). I do use the ethernet port on it for a computer, as its more stable than wi-fi.  How do I update this on the app? The firmware is 1.0.12 Build 221109.

I am experiencing weird issues to be honest, the xbox will say its connected, and apps like youtube will work, however if you run a network check on it, it completely fails and the NAT type is constantly being searched for but never establishes as open, as it was previously. 

I assumed IP/DNS issues due to xbox saying "teredo" as the issue and just randomly not being able to connect. I have tried static IPs etc to no avail. 

Thank you!

  @terziyski 

thank you, I will update this. 
 

However, is it possible that both devices are interfering with each other/the router? 
 

I have tried to connect wirelessly to the WPA4220 and struggled on Xbox, mobile, laptop, etc.

The "main" network ie connecting directly to the smart hub also seems to be temperamental so maybe some issues caused by having all of them? 
 

Very frustrating! 

  @terziyski 

Thank you, there's definitely some more testing for me to do I think! 
 

I'm connecting fine to all 3 today on my phone. The speed is a bit lower on the WPA4220 but not massively.  I assume if this device is providing wireless, it's also connected to the powerline linked to the router? 
 

Are there any settings on the home hub 2 that I should check for the Xbox? 
 

I just want the Xbox connected via powerline as it made a big difference to the experience when I first set it up!