Getting error "Zero gene tables were found to join." with humann_join_table

Hi
I performed analysis with Humann3 and copied gene family files in to a folder to join them in a single table. but I am getting following message:
$ humann_join_tables --input /mnt/f/humann/gene_family --output humann_genefamilies.tsv --file_name genefamilies_relab
Zero gene tables were found to join.

Kindly help me in this.