Why isn't custom business logic working while importing high-volume data?

Set the high-volume import mode to 'No' to run custom business logic. The high-volume import mode is designed to import millions of records at once. This mode doesn't trigger any custom logic configured through the application composer.

For a list of supported objects, see Data Import Options

Note:

If ZCA_FILE_IMPORT_ENABLE_CUSTOM_BUSINESS_LOGIC is set to "Yes", then you won't be able to use High Volume import.