Leaking pond filter aquapro

Desperately need help with leaking pond filter (Aquapro AP10,000UV Pressure filter Filter combo). Leakage bad between the lid and the base unit. It is brand new. Test it straight out of the box as well as adjusting the O ring inside does not make any difference. I am using it with a pump model (AP6000DW). Both the input and output valve is using the same diameter hose. Any help and hint would be great as I am running out of idea on what to do next.