Show all in 3D - The 3D window is completely empty

[cocoloco]

As subject says. Hour ago everything was fine and now I wanted to check something in 3D and there is absolutely nothing.

 Libraries are all  turned on. I also tried zooming in and and out, rotating, and nothing. 

[Barry Kelly]

You are in a perspective view so you may no be looking in the correct direction, even when zooming and rotating.

Right mouse click and 'fit in window.

If that doesn't work, you may have an element very far away from your model.

Select something in plan and show selection in 3D and then fit in window to make sure it is still there.

If it is not then it could be renovation filters hiding everything.

Barry.