I need to connect and building 30m from my house for the internet. It has electricity from the main house system bu there are many outlets around the house and garden. Have tried my TL-PA411 but will not connect. 
At the moment I have ADSL, not fiber, so only 50MBPS

If I finally have fiber (8GBPS) would that help it work or with a more powerful adapter or will the circuit here still be a problem?

Thanks for any ideas recieved.
David.