This is a particularly vague error that Shopify returns when trying to create a lot of products at once on Shopify.
If you see this error, try:
Disabling Images in the Shopify Advanced Options - Shopify is sometimes overwhelmed by the file size of images.
If you continue to see the error, try delisting some products and starting with a handful, then gradually relisting
Once the SKUs exist or are created, you can re-enabled images to get images on the products.