Why is an import process stuck with User Action Required status?

An import process is set to User Action Required status when the process paused because certain dependent data must be imported.

This occurs when the standard service to automate the setup data export and import for a business object which is marked as required for other data isn't available. You must migrate or enter the data manually using another application or process external to the Setup and Maintenance work area. Review the process results to identify the business object and resume the process after you take appropriate action to externally import the required setup data.