Fixed elements don't show when in prototypes shared with a link?

HI there, 

I have just created a prototype for an app. With a fixed bottom tab bar. 

The fixed tab bar is viewable when my phone is teathered to my laptop and when I use the XD app.

However when I share the url link an load it in safari the fixed elemnt is no longer visible, only the main scroll. 

I am hopeing to do some remote testing and sharing a url link to the prototype is the easiest. Is there a way to get fixed elements showing when I shre with a link or is this becase it is effectively a webview that fixed elemenst wont show.

Many thanks for your help