Plutonium

I’ve been trying to play with my friends and every time I invite them it’s an error, I don’t wanna enable UPNP, for security risks. I’ve turned off almost all my security measures just to see if maybe my firewall blocked the connection. Nope. I can port forward because I don’t have access to my router since I share with my upstairs neighbor. They pay for it. And on the server browser I can’t find an empty regular map, I don’t want to play with mods just regular Origins or tranzit. If anyone can help me with this please respond.