Hi,
Just for info I put the dummy code
DATA: t100_lines TYPE STANDARD TABLE OF t001 WITH DEFAULT KEY.
PARAMETERS: p_file LIKE rlgrap-filename DEFAULT 'c:\tmp\test.xls'.
SELECT * FROM t001
INTO TABLE t100_lines.
break-point .
CALL FUNCTION 'SAP_CONVERT_TO_XLS_FORMAT'
EXPORTING
i_filename = p_file
TABLES
i_tab_sap_data = t100_lines.
cross check once if problem persist, share you code so that we inspect and give solution