Few problems translating plugins

Hi everyone,
I tried to translate few plugins with poedit, but the translations aren't displayed. For example, in incsub-support/langages, I took "incsub-support.pot", create a new catalog named "incsub-support-fr_FR.po" and after translating, saved it. Next, I upload the news .po, .mo, .pot files on the site, but it didn't work. I have the same problem with other wpmu plugins. What I am doing wrong ?
Thanks