This article covers
Why am I getting the "Cannot be Blank" error when using Chargebee's Cart-customization?
How do we pass a quantity parameter when the multi decimal is enabled for a site?
Solution
Suppose Multi-decimal support is true, you may get the below error(screenshot) when you are trying to pass only a quantity parameter for per unit item_model.
This error occurs usually in cart_sub_create API.
As Multi_Decimal_Support is true you need to pass quantity_in_decimal parameter instead of quantity.
Related articles and Documentation
What is multi-decimal support in Chargebee? How does it work?
Configuring Multi-decimal Support