Hi @blues,
It sounds like your files may not be Casava 1.8 format. Could you please show some example file names (and does that error message specify which file is in the wrong format)?
You may also want to try importing as a manifest format. Those are flexible to file name format.
I have tried this
qiime tools import
--type 'SampleData[SequencesWithQuality]'
--input-path casava-18-paired-end-demultiplexed
--input-format CasavaOneEightLanelessPerSampleDirFmt
--output-path demux-paired-end.qza
I see — your file names do not fit that format either. Use the manifest format that I linked to above. That format has no restrictions on filenames; however, it does require you to create a manifest file.