Since your data are already demultiplexed, the demultiplexing step isn’t necessary. When demultiplexing, the metadata file is used to look up the barcode sequence associated with each sample, but in your case the barcodes have already been removed and your sequences have been split into per-sample FASTQ files.
Can you provide the wihs_cvl_16s_manifest file you used to import your FASTQ files? My hunch is that you have a sample ID called NA or something, which doesn’t work with current QIIME 2 releases (that issue will be fixed in the upcoming 2018.2 release; we’ll follow up here when that happens). Thanks!
So I discovered that the metadata tabulation step that I was worried about isn’t exaclt consequential - in the sense that it doesn’t contribute to downstream analysis. I realized -after much qiime2 forum reading - that metadata is called for by each script independently. As a result of reading that, I was able to incorporate it at a later step - entirely skipping the metadata tabulate step.
I appreciate this forum a great deal - in the future i’ll do a better job of patiently looking for my answer before posting a “new” question. Thanks!
In the QIIME 2 2018.2 release, Metadata now supports IDs and column names that are NA; this name will no longer be interpreted as missing data, which I think was the source of the original error reported in this topic.