Brand new tap timer leaks around collar

[robers7]

Per the pics attached, I have a brand new tap timer fitted to my outdoor tap with a brand new washer. It always leaks from the bottom of the fitting collar. I have tried four different washers (all pictured), both individually and in combination. I have tried tightening the connection, loosening the connection, applying lots of PTFE-tape, applying a little PTFE-tape, applying no-PTFE tape.. always the same leak. Any suggestions? Most online advice relates the the washers: should I try to source a different type of washer perhaps?

 

[Chuck]

Have a good look at the face on the tap you are attaching this gadget to. It's probably damaged in some way, e.g. cracked, dented or rough. If so, you may be able to polish it flat with some emory cloth and a sanding block but you may need a new tap.