When tried to add a Financial Plan of a project, such as Cost Plan and Benefit Plan, an error message "ERROR You must associate this investment with an entity before a financial plan can be set up." appears and we are not able to add any Financial Plan.
Clarity
In order to add a Financial Plan, you need to specify either "Department" or "Location" to the project. You can set them up as per below.
1. Open the Project and hover the mouse over [Properties] tab. Select 'Settings' under "Properties" category.
2. Set an appropriate Department or Location to each field in the Settings screen.
3. Click on <Save> button to save the change.