This member had that same problem a few months ago:
As you can tell by the title, the issue was finally resolved with a Fusion 360 update. I would check and see if there are any updates available for Fusion 360 and try to push it. The reason I say that is that I used to have a slow internet connection and often Fusion would try to update and eventually give up and never complete the process.
The other thing is you could go to one of the conversion sites, such as https://convertio.co/
and convert the DXF to an SVG. You will want to calibrate the dimensions after importing to be sure that you have not lost some of the detail sizing.
Another option is you could supply your dxf and one of us could import and send the f3d file back to you. You could do that publicly or thru the private messaging of this forum.
I realize these “work-arounds” are not what you were hoping for but I assume that you were previously able to import DXF files and recently lost that ability and want it back. As we found out on that previous topic, none of our suggestions were helpful. Something is probably awry in a file in Fusion 360.