Express mobile app won't export background image

I have been working on an invitation back and forth on my Android phone and my tablet, on the Express mobile app. I saved to my photo galleries on both devices, and on both the background didn't save. I tried sending to Acrobat as a pdf, same thing. All my objects and layers are present except the background. This background was part of the original flyer template, does that matter? My computer is out of commission at the moment so I can't try to look at it there (if you even can, I have no idea if it translates over.) Any insight? It's an invitation, kind of time sensitive. Images attached of original in Express app vs exported. Thanks!