Where are the language files?

The directory is language, not languages

For the JFBConnect component, you can find it under /language/en-GB.com_jfbconnect.ini
For the SCLogin module, at /language/en-GB.mod_sclogin.ini
For social profiles plugins, at /administrator/language/en-GB/en-GB.plg_socialprofiles_*.ini files

If you're still having problems after looking at these paths, I'd suggest re-installing JFBConnect to get them reinstalled. Any configuration settings that you've set will not be altered and will persist on the reinstall. As always, I'd suggest backing up first before doing this.

-Melissa