Getting "Import failed: Check formatting or re-export translation" when trying to import translated XLIFF file in Rise course

Alright, I'm afraid I have the same problem : 

Created a Storyline test course with only a slide > Duplicated > Export xliff 2.0

Translated 100% in Matecat, no tags errors > "Dowload Translation"o r "export xliff"

When I reimport in SL, I get the same error as everybody.

My one and only slide has like only "Translation test" written on it ... And still, it fails. 

Why is that ???

EDIT : xliff to target converter doesn't convert the downloaded file form Matecat ... Maybe Matecat has a problem there ??

Switching back to Word. Really a pity because I like the propagation option a lot ...