When I select file>export>Filmbox fbx, the Fbx Export option screen does not appear. Why? This does not allow me to export Houdini to a FBX file.

Try starting Houdini from shell and see if it prints any errors to standard output.

Also, temporarily rename your Houdini user configuration path and start Houdini so that it can recreate the defaults. See if you can open the FBX export window. If you can, then something in your configuration files is corrupted.

ishinarchitect
When I select file>export>Filmbox fbx, the Fbx Export option screen does not appear. Why? This does not allow me to export Houdini to a FBX file.

which version of Houdini are you using? if it is apprentice then that version does not export to FBX, one of the differences between it and Indie