Please note that reporting is a hierarchical structure and for a lower level to be available for reporting, the level above needs to have its "InReports" checkbox checked. The order of the hierarchy is CompanyDB, BudgetID, OrgUnit, Object and finally Account Number.
In our below example, AccountNumber 000-4100-00" InReports" checkbox is checked. And as it sits at the bottom of the hierarchy, Company DB "DB3147_TWO15", BudgetID "2017 Test1", OrgUnit "000" and Object "4100-00" respective "InReports" checkboxes need to be checked.
In the below example, OrgUnit 150 was deselected.
And you can that it does appear in the dropdown menu.