Hi Laxminarsimha,
After input of basic information for having financial plan in master project just save once (not necessary just to make sure FP is created for master project).
Under tab "Version", you find the default version. Update version type and select the row.
Note: Make sure you are in edit mode of FP.
Now the button "new" will be enabled.
Go ahead with carrying planning cost and revenue in MS AO excel.
Make sure you have installed MS AO in your system and version to be least 1.4.10
Regards,
Pradeep