Hi @Biancabrown! Thanks for the detailed post explaining your problem!
The issue here is that the CasavaOneEightSingleLanePerSampleDirFmt is expecting gzipped fastq files (e.g. foo.fastq.gz), but you are providing non-gzipped files (e.g. foo.fastq).
I think you have two options:
gzip all of your files (one-by-one) - we don’t have a utility for that, so you will need to consult your favorite search engine.
Use a Manifest format! This format is able to gzip unzipped files while importing. The downside here is you need to create a new file (the manifest), which can be tedious.