product-attribute-slug-is-too-long-28-characters-max

There is a solution for this.

  1. Manually create the long name attribute in “Product Attributes”
    page, and use a short slug name here. In the product import
    section there is no “attribute slug” in the Column Headers(Or maybe
    there is one but not used by WooCommerce by default).

    Like so

    enter image description here

    1. Then you can import from CSV files now. No need to change any code.

    Like so enter image description here

    enter image description here

    Hope this helps you.