What should I do if my upload fails due to "file too large?"

For your reference, there is a hard limit on file sizes of import as a QC measure, to ensure that samples are indeed low-pass. To resolve the issue, downsize the FASTQ files to a max 18 GB and resubmit them to the same project. You can do so with the following tool: https://github.com/lh3/seqtk.