CustomPress translation problem

I've been translating CustomPress to spanish. I've translated the custompress-es_ES.po file with PoEdit and then I've uploaded the file to /cp-languages folder by FTP, but the main page of CustomPress plugin appears in english.

The same occurs with content_types-es_ES.po / in /ct-languages folder. I've uploaded the .mo file (not yet complete), but all text strings translated appear in english.

Am I doing something wrong? All the plugins I've translated (and I've translated many of them) work. I don't understand why custom press translation don't.