How do I get my TV back on the Internet?

After my Panasonic TX-43GXM938 television was able to play YouTube videos without any problems the day before, today I get this error message "out of the blue":

connection to network devices is possible, but connection to the Internet is not possible.

My router is the Fritzbox 7560; the connection to the Internet on the PC via cable works without any problems; the internet connection to the notebook via WLAN in the room where the television is located, too. The TV is also connected to the router via Powerline. I get internet connection via PC (via LAN in the same room as the router) as well as via WLAN (notebook) in the same room as the TV. Yesterday everything was still running, not today, I didn't change the configuration of the TV, I don't feel like resetting the TV to factory settings and spending many hours reprogramming the channel search list. Does anyone know advice?

And if you connect the TV via LAN, what happens then? Or does it have Wi-Fi? Possibly. Something is wrong with the Powerline.

Otherwise, try to take the TV completely off the power.

First of all, thank you very much! I don't have a LAN connection in the living room. Powerline works fine with other devices, as does WLAN: I even installed an AVM 600 repeater directly behind the TV, and everything worked smoothly until yesterday. Power off, I'll try it.

Switching off the power for a few hours gave me a few hours of good YouTube video enjoyment; then nothing worked again. I think I have a fair amount of television reception, but the internet browser of my Panasonic TX-43GXM938, which costs almost 900 euro, seems to be a shot in the oven. Without this not particularly working internet stuff, my TV would have cost only half. This as a small purchase advice.