Strainphlan: [e] Parallel execution fails: Ran out of input

Hi!
I’m running a strainphlan analysis following the strainphlan tutorial, and successfully accomplished the first steps (generating .pkl files for all the samples; extracting db_markers; etc). However, during step 5 I am facing the following error:

$ strainphlan -s consensus_markers/*.pkl -m db_markers/s__Ruminococcus_gnavus.fna -r reference_genomes/*.fna.gz -o output -n 8 -c s__Ruminococcus_gnavus --mutation_rates

Thu Feb  1 11:07:35 2024: Start StrainPhlAn 3.1.0 execution
Thu Feb  1 11:07:35 2024: Creating temporary directory...
Thu Feb  1 11:07:35 2024: Done.
Thu Feb  1 11:07:35 2024: Getting markers from main sample files...
[e] Parallel execution fails: Ran out of input
Thu Feb  1 11:07:35 2024: Stop StrainPhlAn 3.0 execution.

Can anyone please help me?

Thanks in advance.