Purchased a Sherwood Avid BCD and the Akona accessory Pro Kit. For some reason, I cannot get the D-Ring and side release clip post pins to separate so I can attach the dive knife sheath. Is there a trick to unscrewing these? I tried two screw drivers, two quarters but just turns.

Often you can use 2 pair of pliers and simply pull them apart. They are just made of nylon and although threaded frequently are stripped by the manufacturer when installed. If you can pull them apart you should be able to reuse them by simply pressing them together again.