I can't add 3d models to my drawing please help!

I have started with a imported cad dwg. and I have drawn all the walls in onto of the original lines now I am trying to add 3d models in and they won’t appear on the drawing ? even if I copy and paste them from another drawing they still won’t show up ? Has this happened to anyone before ?please help

Sorry I have figured it out ! due to the scale of my model the 3d models were literally microscopic ! haha