Only this plugin's japanese translation file doesn't apply correctly

I tried to apply Japanese translation file of pay with a like named pay-with-a-like-ja.mo which is the name when I download the file from WPMU DEV.
However, it didn't work correctly.
I did the same way like another plugins.
So I wan't sure why I experienced this problem.
I have modified wp-config-file to force to load my Japanese translation file as like WPMU DEV's blog.

So I have no idea.

Can you give me any suggestion?

I think translation file's name is incorrect.

Cheers

KAZUKI