Make sure that the files have been properly configured for sharing by opening FileMaker Pro and using the Sharing option in the FileMenu.
If they still do not appear in the Open Remote dialog, the following issue may be to blame:
For More Information see:
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip