Scored Quizzes: When using branching logic with a scored quiz you will not be able to select "calculate result" at the end of the quiz, and instead you will have to select which result people should get for every single branch of your branching logic quiz. 

The reason for this restriction is that with branching logic quizzes the quiz taker does not answer all the questions of the quiz, which then makes the results ranges set up in the quiz no longer accurate. 

To use branching logic with a scored quiz you have to manually select which result your quiz takers will get for every single branch in your quiz.

Assessments: When using branching logic with assessments you will not be able to select "calculate result" as the result given to quiz takers and instead you will have to manually decide which result your quiz takers will get for every single branch in the quiz.

The reason for this restriction is that when a quiz taker takes a branching logic quiz they will not answer all of the questions and the results will no longer be accurate because the results ranges are based on someone answering all of the questions of the quiz. 

To use branching logic with assessments you will have to manually select which result your quiz takers will get for every single possible pathway of your quiz.