Events Manager [Button registration form on Apple] won't work

Hi,

I use the Event Manager on this page and on PC everything works fine.
https://www.makeup-studio.com/#!/veranstaltungen/

But on Apple, the Button of the registration form does’t work.

Whatelse does iOS do what the PC doesn’t (or vice versa)?
Can it be an Theme issue although it’s only a Mac problem?

Thanks for your help, Andrea