Hi there,

If you can only get 25MBps even with hardwired connection, there might be big interence on in the electric wiring.

You can try to unplug some big electric equipment such as refrigerator and check if it can improve.

Also, you can do a test  by just putting the two device into the same room ,and hardwired connect your PC to the extender and check if the speed is good.

If the speed is good, which means it is influenced by the electric wiring.

For more troubleshootings ,you can click on the following link to get some help:

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

Merry Christmas!