You've met all the requirements for YouTube merchandise, opened a Spreadshop, created your first products and prepared them for import to YouTube – and still your merchandise doesn't show up on YouTube?
YouTube checks compliance with community guidelines
YouTube checks every product that’s imported into your merch shelf. This is done to make sure your merchandise meets YouTubes’ community guidelines. This process can take three to five days. It’s possible that your designs are already online at Spreadshop, but haven’t yet been published on YouTube (or just partially). Have a little patience.
The progress of the merch review can be found in your YouTube studio in the monetization tab. If your product was rejected because it was against the guidelines, you’ll also be informed there.