Well as far as I know on all of the Connexions/Connections before v4 and on all of the original Tamagotchi, you need to turn out the lights for it. There are also some other Tamagotchi that require the lights been turned out for it- Odenkun, Keitama, Keitama Akai Series and the original Tamagotchi Plus, maybe there are more. On all of these versions there is a special icon to turn out the lights. On Tamagotchi Connexion/Connection versions 1-3 it was kinda like a lamp.
The v4 does not have that icon. Here is a screenshot from that link that the V4 gave us. (By the way, "the V4" is the user I'm talking about.)