3rd party prefab download/upload/drop issue

I have bookmarked and saved a bunch of prefabs from main menu in forge but when I try to drop the prefab into the map it doesnt do anything and the prefab doesnt populate on the map what do i do am i doing something wrong anyone have any solutions??

Make sure you got plenty of room to spawn it , it will say whether u do or not theres been countless of times where i thought i had enough room and i didint, goodluck !