hierarchy of bex query can't work

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Hi expert,

      I am using a bex query for WEBI report, field cost center has a hierarchy. but when I load bex query into webi, this hierarchy item is displayed with check mark on right-top of the hierarchy flag. once I put this hierarchy into result fields, I can't even display and select its member and level. but for other hierarchy of other field, display and selection are normal. please tell me why ?

Many Thanks,