Have you looked at the using a tilemap section of the documentation? When I have followed the steps exactly and made my node setup the same as in the documentation, I have been able to successfully get collision with a tilemap.
I think for exported tilemaps to have working collision, the tiles have to be set up in the following order: Sprite -> StaticBody2D -> CollisionShape2D/CollisionPolygon, but I do not use the 2D side of Godot very often so I’m not positive.