Did you look into the log file winfig.log? It's in c:\Users\<username>\AppData\Local\Temp\
Perhaps there is something in there.
The correct commands for a file named foo.fig would be first to create the graphics part:
fig2dev.exe" -L pdftex foo.fig foo.pdf
Then to create the LaTeX part:
fig2dev.exe" -L pdftex_t -p foo.pdf foo.fig foo.tex
Note the -p foo.pdf to add the overlay to the LaTeX.
The message about "Untested Windows version 6.2" comes, because Qt 4.8.3 is from 2011. But it should not actually prevent WinFIG or fig2dev from working. However, the next WinFIG will include a more recent version, either 4.8.4 or 5.0.1.