You have to install the cable on the right place on the case.
Don't connect it !
Turn on you iPad (i know, it´s not correct to work with it turned on, but it´s easier), and unlock it.
Insert the cable on the conector and as soon the iPad detects it, lock it place.
(If you connect the cabble all the way to the bottom, he will not work. Only works half way.)
Test all the functions.
If some don´t work, try to gently move the conector backward´s and forward.
it´s not hard but it requires a lot of pacience.....
(Sorry for the rudimental English, it´s not my mother language, but i hope to help).