Odata entity relationship with 404 error: Resource not found

Dear friends,

         I create an odata service with entity relationship between two table, the code like this :

service namespace "ANA_SO_HEADER"

{ "BOOK"."ZSOHEADER" as "HEADER" key generate local "GenID" navigates ("Items" as "SOITEM")

    ;

   "BOOK"."ZSOITEM" as "SOITEM";

   association "Items" principal "HEADER"("SaleOrderNo") multiplicity "1"

   dependent "SOITEM"("SaleOrderNo") multiplicity "*";

   }

I can check both HEADER and SOITEM entity, but I can not visit the item entity of the header hyperlink, it have this error : Resource not found.

Is any wrong with my odata service code  or my table data ?

Best Regards,

Zhang