You can trace where your DNA is going. You know there is a band of input DNA. Sample all of the flow through, wash, and elutions and run them on a gel. Somewhere, your DNA is hiding. You might want to try this with a DNA sample which is easier to produce -- the problem is likely not specific to your DNA sample.
ethanol has already added into wash buffer (my colleague did it). sorry for earlier misunderstanding.
How should i trace the hidden DNA? i don't understand clearly, should i load the binding solution and wash buffer trash onto the gel?
the generated band is not in a bright intensity. then i thought to dilute it in a less TE/water/elution volume. but, both PCR and gel clean up were still the same. not any progress revealed.
meanwhile, when i worked with 16S primer, things gone just right. i had no problems in a pcr purification stage.