Same issue happen to me last night. You need to accept new PSN T&C after updating system v5.0.

Method 1
Some said that you need to go to Friends and change Privacy setting > new T&C pop-up > accept it.

Method 2
Logout PSN and sign in again.

Method 3
Change PSN password.

Method 4 - Worked for me
From the PS4 Menu (XMB), scroll right to Settings > Network > Set Up Internet Connection > Select either Wi-Fi or LAN cable (Wired) Wi-Fi: Custom > Select Network > Enter Password (automatically saved if you are already using this network) > IP Address Settings (automatic) > DHCP Host Name (Do Not Use) > DNS Settings (Manual) LAN (Wired): Custom > IP Address Settings (Automatic) > DHCP Host Name (Do Not Use) > DNS Settings (Manual) From there, enter the Primary DNS as "8.8.8.8" and the Secondary DNS as "8.8.4.4" Next > MTU Settings (Automatic) > Proxy Server (Do Not Use) > Test Internet Connection

*If the above DNS server does not resolve the issue, try the following server instead: Primary DNS: 208.67.222.222 Secondary DNS: 208.67.220.220

Used the above mentioned method 4. Prob solved for me 

Tx
EDIT : I managed to sort out the problem with the method but , in FIFA weekend league , i was not able to find games as every time i find an opponent it will give me an error "You connection to your opponent has been lost".

Then , i setup a new connection without the DNS settings and i was able to find games again. Just sharing , in case someone from here cant find games in FIFA 18.