Hi@gregz,

Thank you for contacting our community.

If you're experiencing low speed issues when connected to a TP-Link powerline device, there are several potential factors and troubleshooting steps you can take:
    1. Check powerline adapters' placement: Ensure that the powerline adapters are plugged directly into a wall outlet and not into power strips, surge protectors, or extension cords. 
    2. Test different electrical outlets and move them into the same room for comparison.
    3. Check powerline rates between the powerline devices via tpPLC utility/App, you could refer to this FAQ to understand the difference between powerline rate and actual internet speed: Explanation about the Powerline Rate and Actual speed of the Powerline Adapters
If the powerline rate is too low, refer to this FAQ to see if it will be better: What can I do if my powerline rate is very low?
    4. If the wired speed is normal, only wireless connection is slow, please try to change the Wi-Fi channel and channel width on the powerline extender.
 

I will send the previous firmware via Message to you, please note that nvm and the corresponding PIB need to be upgraded together and cannot be used together. 

Please refer to How to update the firmware using the tpPLC Utility on Windows