Importing Drawings ( DXF,DWG ) in Altium
There are two things I can think of that could be your problem:


You set the wrong units when exporting the DXF/importing to Altium. Make sure if you use mm in one, you use mm in the other. Otherwise your scale will be all wacky and the DXF could be too small to be visible
The origin of your DXF is in the wrong place, and the DXF is pushed way off your screen. Scroll out in Altium and see if you can find it.


Your most likely problem is the units. I see you're working in mils in Altium. Make sure that the DXF is exported with mils as the units.