Power down your PS4, router and Internet modem/gateway. Unplug all three devices from power and leave all three disconnected from power for at least 5 minutes. After 5 minutes power your network back up, then your PS4. If the above doesn't resolve the issue then you'll need to log out of your PSN account on your PS4 and then power it down. Then go to playstation.com using a computer or mobile device and log in to your account. Once logged in go to your settings and select the change password option. Change your password to a new one, log out, then log back in using the new password to verify it works. Now power on your PS4 and then log in using your new PSN password and try the game again.