When using the Reimbursable filter on the Employee Expense report, sometimes employees submit that report to their manager for approval. If the manager is set up to see only the projects and employees they manage, they cannot see the complete expense report (unless they have access to all projects).
Typically, managers are allowed to access the data of the employees they manage. In such a case, the Expense Entry module in Security has the option checked: 'Allow access to employees I manage'. However, you need to get the other security permission also checked: 'Allow access to entries of projects I manage'. This allows the manager to see the expense entries of all the employees being managed with no project restriction because it is based on what employees log as expense entries.