Smart TVs and sticks rely on Wi-Fi, and their built-in radios are weak compared to a phone. A TV that works in the living room may struggle one wall further away, and a stick hidden behind the metal body of the TV gets an even worse signal.
Streaming sticks have a second common failure: power. A stick plugged into a TV's USB port only runs while the TV is on, and an underpowered port makes it reboot and drop the connection at random.
Network forgets happen too. A router reboot can leave the TV still holding a stale connection, so it shows full signal but loads nothing.