2nd router for the internet?

Hi, I'll explain my problem in detail now. Two days ago I reset our WiFi and set it up again because we were constantly having problems with the connection and so on. Then I wanted to connect my own WiFi route upstairs in my room, which is where I usually have my LAN cable for my PC. The router works just like before, but when I plug in my LAN cable and start up my PC, I have no internet. Strange, because as I said, it always worked before. Then I noticed something else: the router is no longer displayed with the same name on my cell phone as the other one, but with a different name. Can you perhaps help me?

Thanks in advance