PS4 Multiplayer - Not able to connect AT ALL - "You have lost connection to the session"

[legs76]

Since day 1, I've not been able to get into a single multiplayer match on PS4, either through Quick Match, or the Server List. Every single time it starts the process of joining a match, but ALWAYS ends in Error: You have lost connection to the session. I know some people have messed around with putting their PS4 in the DMZ on their routers, etc. but this shouldn't be the case.

I play Killzone and AC Black Flag multiplayer without so much as a single problem and my PS4 connection test is 100% A-OK with a NAT Type 2, 50+mbs down and 10+mbs up - hard wired via ethernet. 

The whole thing is getting a bit ridiculous.