No internet on smart tv?

When I try to open apps like Sky, Prime Video or YouTube on my TV, I get a message that my Wi-Fi has no internet access. The Wi-Fi works fine on my cell phone and other devices. Strangely enough, Netflix also works on TV. I would like to know how I can solve this problem so that I can also watch YouTube and co. Can look. What can I do?

Does the LAN cable (or the WLAN connection) have internet? Some routers first deny new devices access to the internet before this has not been approved by an admin