Could you have uploaded an older version of the zip file to the fabricator? Or try another fabricator, it’s usually free to upload a design and preview before paying.
Another thing to watch out for: Changing project name or file naming format (Protel or not; Protel filenames are not necessary for JLCPCB these days, some tutes are outdated) between generating gerbers, resulting in a directory with a mix of old and new gerber files. Best to nuke the gerber directory before regenerating the files.
Also JLCPCB supplies a plugin for submitting jobs which takes some hassle out, find it in the PCM. You never told us what version KiCad you’re running, hopefully it’s the latest in v8.
This FAQ explains what you have to do to increase your trust level be able to post attachments:
Or wait for a moderator to promote you. When you can post attachments, post the entire project, whcih can be created by archiving the project in a zip file. The settings are part of the project and may affect the visibility of silkscreen items.