Well, that sure is not a helpful error message! One thing you might try is uploading your fastq.gz file(s) to galaxy as a data collection then importing that collection as your SampleData[PairedEndSequencesWithQuality]. Some more instructions on how to do that can be found here with someone having a potentially similar issue (Basically sometimes QIIME 2 and Galaxy disagree a bit on the specifics of what a given thing should look like).