There’s two ways of exporting a DXF.
One is the top task bar there’s an export out up there where you can either do a fd3 export or a DXF export.
The other area you can export is if on the left sidebar you right click on your sketch and there’s an export DXF there.
I’m not sure if both avenues are turned off or not in the free version.
What can you export?
If you can export your fd3 file zip it and post it on here I could pull a DXF for you and repost it.