Why no fluid collision on imported static mesh?

This is in the content example fluid map. Why is the cow and unreal sphere (top left) interacting with the water but not the quixel buckets, pots, bowls (boulders work fine), and also models I imported from maya not having water collision either (3 on the right). collider tag is set, and I tried creating collision in the mesh preview along with changing complexity type, but nothing happens. Please help