Can't connect to ethernet cable

So I have found this question, but never a clear answer or one that worked..

I connected my ps4 to a lan cable, cat5e patch cable, and it says it isn’t connected. The first time this happened was when I bought a switch, because I have 1 cable going from down to upstairs, and I needed another one for the ps4. Tagging another one through walls is just too much trouble, so i just got a cheap switch.

I have gamed on that one cable on the ps4 before I had a switch, and it worked just fine. That cable comes directly from my modem. I tested different cables through the switch and none of them worked. One kind of does, but it disconnects randomly 2 minutes which kicks you out of online games.

So I did some testing, put the ps4 downstairs and connected all the cables i have from the modem to the ps4, including the 2 new ones I bought especially for this, and none of them worked. Not even the one that kind of connects through the switch.

In my boyfriends house it works just fine, from the modem and the wifi extender. I would call the company where the modem is from but theyre closed in the weekends and thought maybe someone could help with it.