Mapping Items for Netsuite Item Receipt

This is a really common use case, and there is def a way to do it; but it is difficult to say why it is not working for your flow and/or CSV file. You might want to get some quick help from support.

The only idea I have from the pics above is to try setting "Items: Replace All Lines" to true.

You might also find something useful in this post.

Good luck!