when connection drops, the powerline light on the adapter is on or off? Have you recently purchased any new electrical devices? And if you connect the PS4 to your router via cable, can you play games?

Hi,

The lights always stay green on both adapters. No new major electrical products - I can play the ps4 on the Wi-Fi and directly connected by ethernet to the router.
When on powerline, my ps4 online account signs in but I cant then complete matchmaking or join any servers etc...

are they in the same breaker? can you try different location or sockets to test? if no changes, it's suggested to submit a ticket to TP-Link support.