Import data to Periods with Data Management

Summary:

Content (required):

After a successful data load workbench in Data Management, I try to execute data load in a specific period going to "Application" --> "Periods" --> "Import Data". Once I import data and refesh the page, it gave me an error: "Unmapped Accounts" as in the screeshots. How could i fix this error?

Thank you in advance for the help.

Version (include the version you are using, if applicable):

GEN2, Enterprise Cloud Service version

Code Snippet (add any code snippets that support your topic, if applicable):