fragment_head is not returning any Value

Hi,

While doing Reassembly in my dissector

fragment_head *fd_head; i have assigned. After declaring table

  fd_head = fragment_add_seq_next(&mte_reassembly_table,next_tvb, offset_payload, pinfo, 0, NULL,  28, TRUE );
if (fd_head != NULL){
col_append_fstr(pinfo->cinfo, COL_INFO, " MTE segment of a reassembled PDU");
} else {
       col_append_fstr(pinfo->cinfo, COL_INFO, " Something Wrong");

}

next_tvb is a originnal TVB and offset_payload is Not a Zero . seq id set to 0 and data is NULL and 28 is the length and more_frags set true.

Iam always getting the colinfo as Something Wrong. i have tried using fragment_add_seq_check, fragment_add_seq but still same. Can anyone help me why iam not getting the fd_head?

My table initialization all ok. comparesd with other dissectors.??

Please Help!