I downloaded the mobile version today and I am unable to export shared photos. When I try to it tells me "couldn't complete, cellular data usage disabled" even though under preferences, it's completely greyed out and won't let me enable it.
I'm not generally an Android user, but a quick Google offers a possible reason... go to Android Settings > Wireless & Networks > Data Usage > Network Access and it looks like you can block cellular data for specific apps. See if it's disabled there?