Import failed - the text could not be read from disk

I bought the app Yesterday, since then I tried to upload materials as draft but nothing is coming through. I systematically got the “Import failed. the text could not be read from disk” message. Weirder, it actually works for one of my document for no apparent reason - same emplacement, same format, same size - but not for the others.

My files are originally open office documents; with text and images, converted to Rich Text for the sake of scrivener import - again, I followed the specifications.

I set up my dropbox file correctly as directed and even download the app, just to be sure.
I’m starting to get really frustrated as I didn’t even had the opportunity to try the product because of this issue.

Is there something I do not see here?