No more full screen on my phone

Hello DYWM ! I’m a new subscriber from Switzerland and I’ve had a slight problem since my subscription (or maybe since the website was down this past week ?). As I practiced your classes with my phone, I used the little purple arrow on the right side under the screen, to obtain a full screen. But this arrow seems to have disappear… now I have only a 1/3 of the screen on my phone.

By the way, thank to you all for your amazing classes !

Laura, Geneva