Unidentified network and no valid IP configuration?

Yesterday, while watching Netflix on my PC, my internet suddenly went out. I assumed that my father once again set up an internet block via the Fritzbox, but since it was still the case this morning when I had to go online, I could rule it out.

The following is shown to me when I click on the icon: "Unidentified network" and "No Internet access".

So far so good. I tried my luck with the cables and reset the LAN adapter, but without luck. Then I tried a Windows troubleshooting, and it spat that my Ethernet does not have a valid IP address. Okay - but why, and why did that happen so suddenly yesterday? I made myself smart on the Internet and after a while I found out for myself that the DCHP server might be the cause. But since all other devices in the household are perfectly connected to the Internet, I was able to rule it out again. I also reset the IP via the CMD prompt, but still without success.

Among other things, I tried things like reinstalling the driver, restarting the DCHP service, restarting the PC several times and trying to manually assign an IP address to my PC, but all without success.

There's no viable solution to this problem on the Internet, and I have two problems at once that I have not found on the Internet. I assume that it is actually a hardware defect - the PC is no longer the latest. (From 2009 - still runs like clockwork)

If you have an idea how to solve the problem, it would be very nice if you could tell me.

If available, you could try a WLAN adapter (USB). If it works with it, the network card is probably defective. Happens rarely, but does happen.