Demultiplexing error

hi, I am running codes for microbial analisis. I am in the step of demultiplexing. I run this code:

prep_fastq_for_uparse_paired.py -i cutadapt_R1.fq -r cutadapt_R2.fq -b Undetermined_S0_I1_001_A.fastq.gz -m maping_file_ALL.txt -o demultiplexed_seqs_16S/

I got this error:
Start time: 2021-10-21 14:31:43
Traceback (most recent call last):
File “/software/helper-code-for-uparse-master/prep_fastq_for_uparse_paired.py”, line 166, in
main()
File “/software/helper-code-for-uparse-master/prep_fastq_for_uparse_paired.py”, line 52, in main
barcode_dictionary = create_barcode_dictionary(mapping, rc)
File “/software/helper-code-for-uparse-master/prep_fastq_for_uparse_paired.py”, line 97, in create_barcode_dictionary
raise ValueError(“Duplicate baarcodes are not allowed in the mapping file.”)
ValueError: Duplicate baarcodes are not allowed in the mapping file.

any ideas on how to fix it?
thanks