Hi Kingsuk,
If the flag Vendor sub-range relevant is not checked then you cannot create sub-range for the Vendor. Both the buttons different data and sub-ranges are in disable mode.
Please check the changes for correct account group by selecting extras --> Administrative data.
For details, please read the section pre-requisite in the link below.
Vendor Sub-Range in Purchasing - Purchasing (MM-PUR) - SAP Library
BR, Rosh.
