Thank you for the suggestion. I am still getting the same error after downloading with the --origfmt option. Maybe this particular dataset was uploaded without flowcell IDs?
$ fastq-dump --split-files --origfmt --gzip SRR12623869
$ mv SRR12623869_1.fastq.gz SRR12623869_S1_L001_R1_001.fastq.gz
$ mv SRR12623869_2.fastq.gz SRR12623869_S1_L001_R2_001.fastq.gz
$ ./txg fastqs upload --project-id <myProjectId> ~/pathToFastqFiles/
There was a problem preparing your files for upload.
target "SRR12623869_S1_L001_R1_001.fastq.gz" is not a valid FASTQ file (could not parse flowcell ID: not a valid fastq)
target "SRR12623869_S1_L001_R2_001.fastq.gz" is not a valid FASTQ file (could not parse flowcell ID: not a valid fastq)
$ gunzip SRR12623869_S1_L001_R1_001.fastq.gz
$ head -n 20 SRR12623869_S1_L001_R1_001.fastq
@1
GGTTGTAGTTGCCAATCCATTGCGTA
+1
FFFFFFFFFFFFFFFFFFFFFFFFFF
@2
GAGGGTATCACTCACCTCCTTCTTAG
+2
FFFFFFFFFFFFFFFFFFF:FFFFFF
@3
ATCCATTGTATTTCGGGATCACATGC
+3
FFFFFFFFFFFFF:FFFFFFFFFFFF
@4
CTCCATGTCGTCCTTGTTAGTTGTCA
+4
FFFFFFFFFFFFFFFFFFFFFFFFFF
@5
ATTACCTTCGAGTACTATAACTTCCC
+5
FFFFFFFFFFFFFFFFFFFFFFFFFF