Translating Invoising

Hello, Stiofan!
This can be funny, but I can’t translate the Invoising plugin into Russian – the translation does not work. I translate with poedit.
It seems I checked everything and everything is correct.
What have I done:
The language file of the plugin was saved as invoicing-ru_RU with the encoding of utf-8;
Changed the language to Russian;
Checked in Notepad ++ – encoding utf-8 without a bom;
Properties of the language file – ok
Coincidence of the lines in the translation with the code is ok;
I even looked at the code in the file class-wpinv.pxp – ok;
What should I do?
By the way, the translation files of the GD on my website work fine