I believe that the Ethernet connection on Sony TV's is capped at 100mbs, which is fast enough for most streaming apps. If you need a faster connection (Bravia Core, don't think available in NZ yet) you will need at least 115 mbs to stream their best quality. So wi-fi is the only way to get that speed on Sony TV's.
Unplug the ethernet connection and try connecting to wi-fi 5