sales tracking scripts don't work for mobile sales

Hi support
I have google analytics' ecommerce tracking script entered in the section RC/marketing/external sales tracking/sales tracking scripts. this tells my google analytics page when i get a sale, its ID and revenue. It works fine on sales made on desktops and tablets but doesn't work for mobile sales. I've had 5 mobile sales in september but analytics says i've had none. can you suggest anything i can do?
thanks
jonathan

thanks support, my store id is 46544.
i have modified the hosted cart pages for shopping basket and checkout etc by editing the default versions so they incorporate my logo etc.

Thanks Support, but am i correct in thinking that your implementation of analytics doesn't support cross domain tracking? In which case, if i follow your implementation and remove my code, won't I lose the ability to see the source of my conversions because a customer using the cart will appear look like a new visitor to analytics, rather than one passed from my website?

ok thanks support, have now implemented and GA successfully tracks from my domain to RC as you said. however the snippet of GA tracking code which i pasted onto every page of my site needed to differ slightly to facilitate cross domain tracking and to track the use of forms.

In case anyone else is reading this, google's article on implementing cross domain tracking is here - https://developers.google.com/analytics/devguides/collection/analyticsjs/cross-domain#autolink.

The snippet i have pasted on every page of my site (which is working, and which is slightly different to the snippet RC offers when implementing Universal Analytics) is as follows;

<script>
(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,'script','//www.google-analytics.com/analytics.js','ga');

ga('create', 'UA-XXXXXXXX-X','auto', {'allowLinker': true });

ga('require', 'linker');
ga('linker:autoLink', ['romancart.com'], false, true);
ga('send', 'pageview');

</script>