okey, you followed the tutoriel here I guess!!
At some point your are asked to change the headers of your Biom-taxonomy.tsv from "Feature ID Taxon" to "#OUTID taxonomy" okeyy with keeping the separation between OUTID and taxonomy as a tab (not space or two spaces etcc). For me that was the problem when I modified the headers the text editor that I used did not save for me the tab separation.
Hope I was clear.
Manil