Pentair - 261185 Tagelus Top Multiport Valve 2" TA 100D Clamp with 8" Neck - 261185 . Bottom half coming apart

I have a 2 year old Multiport valve that I removed when changing sand. It's not staying together when I try to mount back on filter pipe. Should it be glued? I see a notch but that's not holding it together.