Like with most awards shows on Nickelodeon and MTV the winners are announced long before the telecast. This ensures that big stars who show up get an award. Jennette actually received more votes than eventual winner Ariana Grande but was told that she would not be receiving the award because of her photo leak scandal. She was also told that if Sam And Cat returns, which is doubtful at this point, that her contract would not be renewed. Dan Schneider could have saved her but chose not to. He is more concerned with looking after himself and finding fresh female talent.
Jennette boycotted the show and Miranda boycotted (even though she was told she won an award) right along with her. When Jennette asked Ariana to also boycott the show Ariana refused. Jennette immediately unfollowed Ariana on Twitter and was a no show at the awards.