I am having issues when I import, this is what I have done. Only one size gets imported
Your mapping was not correct, you should use Fixed Line item only if you want to import data to particular line item, here you want to import data for more than one line items so you have to use column header for all line items.
if the name of the line items is same as your import file then it will automatically mapped.
Hope this helps!
the import is correct, you can see the page selector is set at all products which is the top level for products list, i.e summary, so the line items will be seen based on the summary method in the blueprint view for the line items, which is none int his case, hence you dont see anything at all products (i.e top level), change page selector to view any product, you can view the data, because import is successful