Common Data Service allow you securely store and manage data that is used in the Business Applications.
Data within common data service is stored within set of records called entities. An entity is a set of records used to store data, similar to how a table store data within the database.
Entities – Common Data Service
Issue: Data Entity of Dynamics 365 for Finance and Operations is not available on power apps and Power BI
Casue: Data Entity of Dynamics 365 for Finance and operation will not be available if Is Public property of Data Entity is No
Resolution: Just change the Data Entity Is Public property to Yes