I assume the fibre goes through some form of box (probably a fibre to Ethernet modem) so that you have an Ethernet to connect to the router.
You are connecting the modem through the Powerline adapters to the PS4. When you do this you lose some of the functionality that is provided by the router. Apart from the obvious function of allowing multiple devices to share the Internet connection, by leaving the router out of the network you will be removing some of the protocol that the router provides for establishing the connection with your ISP.
Although I normally use a router, at one point I had a router and a separate modem, and I connected a PC directly to the modem. I had to go through extra steps in setting up the PC so that it provided my ISP username and password to establish the Internet connection. Normally, my router has this information stored in its settings and it logs on to the ISP automatically.
In your living room, where the PS4 is located, try installing the router so that the WAN port on the router is connected via the Powerline network to the fibre port (or modem), and then connect the PS4 to an PC/LAN Ethernet port on the router. I suspect this will work and the PS4 will go online. This will confirm that the router is providing the missing protocol component in connecting to the ISP.
I don't know whether a PS4 has the functionality to log on to the ISP. If it does not, then you are probably stuck with having to go through the router. It should make no difference which end of the Powerline network the router is located as long as its WAN port is towards the fibre connection and the PS4 connects to one of the PC/LAN ports (or even WiFi).
I hope this helps.