Shapr3D viewer for ipad

Why is it that the native format of Shapr3D file does not show an image of the design when viewed on the iPad(not from within Shapr3D).
STL files are shown perfectly.
I don’t use the pictorial storage as a very simple list of newish first is useless for my needs. So I save designs in the native format and when I want to continue I import it into a new file. This approach allows for version control and filing in folders.
As I say the only issue is the files do not show thumbnail of the design.
Can you help.

Are you talking about icon views within the Files app?