I  bought a home with a in-ground pool that has a Cristal-Flo II top mount sand filter, model 145360. I took the valve assembly off to check sand quality and levels. I discovered the gasket needed replaced at the flange. Replaced it with a pentair factory part, lubed it, and attempted to put it back together. The flanges won’t mate close enough so I can apply the two collar halves. Tried reapplying silicone lube, but no luck.

Any suggestions?