Gravity Forms contact form doesn't show on mobile devices

Hi,

The Gravity Forms contact form on this site doesn't show on mobile devices (at least not on a iPad and Android phone):

=> http://stressuitfocusaan.nl/contact

On other sites from our clients the forms does show up, for example:

=> watwerktwerkt.nl/contact

(These are multisites.)

Any idea what causes this and how to solve it?

Thanks in advance.

Andre van der Goot