Flip Adapter Won't Fit My Port

Hey all

I recently purchesed AOI Flip Adapter for my Fantasea FA6500 housing.

It's suppose to fit the port but for some reason it's not (FML Flat Port 34).

Does anyone with the same port and adapter had the same problem?

Is it just me not knowing how to put it on the port?

Thanks to the helpers

The description says it fits most M67 threaded ports,  There should be a male M67 thread you screw into the mating thread on your port.  It mentions it comes with a retaining ring wrench which looks like it has lugs to allow you to screw it on.  The only thing that might stop you is is the threads on your port are recessed a lot or looking at your port the rim at the top is very wide which may interfere with getting the thread started as it looks like the the thread is in a U shaped recess that would need to fit over the rim of the port. 

I would contact your supplier if no one else replies with suggestions.