Hi Venkat,
The field is grayed out as a result of there not being any field you can edit on planning screen. Please see the attached screenshot from some test data in a sandbox system that illustrates this. As you can see in the first screenshot you can click the button but in the second I cannot. As far as the "Reopen Rejections" button this is likely grayed out as a result of there not being any records in "Rejected" status. If there were then I imagine this button would be clickable.
Are you using the OADP to define your own fields on the Compensation Planning screen? If so, did you make sure to tie the editable fields (Amount & Percent) on table V_T71ADM30 to a data field so the system know which field we are editing on MSS matches in SAP on the Infotype 759 record.
Please also make sure the check box is selected for "Column ready for input"
This particular setup for the OADP in relation to the following location at the IMG --> Personnel Management --> Enterprise Compensation Management --> Compensation Administration --> Settings for User Interface and Process --> User Interface for Compensation Planning --> Planning Table
Thanks,
Imran