It is better to use an earlier MetaPhlAn with HUMAnN 2.0 or use the 3.0 versions of both tools, as described here:
https://forum.biobakery.org/t/announcing-humann-3-0-alpha/518/2
If you already have a taxonomic profile from MetaPhlAn you can pass it to HUMAnN via the --tax-profile flag (i.e. you don’t need to rerun MetaPhlAn as the normal first step of HUMAnN).