If you are plugging a ethernet port directly into the wall it means the apartment complex has equipment in the path to the internet. You can only go 100 meters on ethernet which is not enough to reach off the apartment property.
This is very hard to say since there are so many variations in how apartments setup internet. The key thing would be the address your computer was getting when it was plugged into the wall. If you issue a IPCONFIG command you should see the ip address. I would use a site like whatsmyip and see if the ip you see matches what you see in your pc. If it does not then there is a router doing NAT in the path. You can not have 2 routers (ie yours and the apartments) and get things like port mapping and UPnP to work.
If the ip matches then the problem is something strange with the router. It should work to do UPnP, you could also try to put the PS4 in the DMZ.