Elements copied/inserted on plan not seen on 3D

[DanInMiami]

Hi in two or three models I'm having a problem where groups or model elements that I copy or insert in plan do not show on 3D. I've been having to copy them from plan, deleting them and pasting in place on a 3D view so that I can see them on 3D. What gives?

[Dimitri Harvalias]

Some objects are not visible in 3D. Drafting (detail) lines or other view specific elements will only be visible in views in which they are placed. Model lines are visible in 3D views as well as 2D views.

[patricks]

He said he is pasting them in place in the 3D view and then they show up, so they must be 3D model elements.

If it's a workset file, perhaps your current active workset is turned off in your plan view, but turned on in your 3D view. Copied objects always go on the active workset, not on the same workset as the original object (which is frustrating sometimes).