Etsy can reject your listing and return this error "You have already created the maximum number of shop sections".
This error occurs when the listing you are trying to create and the Etsy shop section you have provided for it will cause it to exceed the number of custom sections Etsy allows. Etsy allows up to 15 custom shop sections including the default All Items section.
To resolve this error, edit your listing and delete the shop section you provided, or use an already existing shop section, then save and publish to have your listing successfully published.
Contact support at firstname.lastname@example.org if issue persists.