Minecraft won't work on split-screen?

Depending on your console, you might have to change it's settings outside of the game. If you have a PS3 or PS4 it's easilly accessable from the dashboard (sorry i don't know what it's called I used to be a PS3 fan now i'm a xbox gamer), same with the Xbox. On the Xbox 360 what I do know if that you go all the way right (on the newest dashboard update) you can change settings there and if you go to system there's one tab there that should do the trick.

Check both controllers

Check your device properly check all the wires connection an if still it doesn't work than contact your nearest device mechanic