Branching in a Quiz

Hi.

I have created a quiz which has 14 questions.

I have then added the 'Branching' option. For example, on Q2 I have clicked on branching and selected Q4 from the drop down list.

However when I preview my quiz, it looks no different. Nothing happens when I get Q2 correct.

Am I doing something wrong or misunderstanding the function?

Here is my quiz if it helps:  https://forms.office.com/Pages/ShareFormPage.aspx?id=ojMEGUnO_EOVbqqIrp1XKISV4YrQC3tAh5WOvuzRo55UNUFGSU9VUTRWRDVaT0tHTklYTlpIWDIzMS4u&sharetoken=vjy0hV9hw3XzJxsZfvwZ 
Thanks for any help you can give!