@kadonx 

Hello, 

Firstly, please follow the below instruction to narrow down the issue and tell us some details:

https://www.tp-link.com/en/faq-2231.html

a. The speed you can get from PA4010 when it is in the same with the main router.

b. The wired link speed of your computer, how to get it: https://www.tp-link.com/en/faq-2265.html

c. The powerline link rate which shows up on the tpPLC utility.

d. The speed you can get from the main router by wired cable with the same computer.

Any updates, just let us know.

Good day.