I'm using debut theme, and i keep getting this message when checking out. Uncertain how to fix this issue and yes all products have shipping weights.
You should only be seeing that area if your in the theme editor trying to checkout, it shouldn't affect customers.
@BenChai "said that the store was didn't have a checkout setup." is not the same as a specific error message that commonly appears in the theme editor.
Get exact feedback, or provide urls for others to reproduce the errors.