A priori Photomatix ne gère les RAW du 6D qu'à partir de la version 4.2.6, voici un extrait de leurs FAQ :

Does Photomatix support Raw files from the Canon 6D and G15, Nikon P7700, Panasonic G5 and Sony Alpha A99 and NEX-6?
Yes. Support for Raw files from these camera models was added in Photomatix Pro 4.2.6 and Photomatix Essentials 3.2.2.