Translation not Loading

Hello Tim.
I just have installed the plugin Simple Membership.
The plugin was already installed in my language but the thing is that the translation is not loading. I have checked the default .po and .mo locations which were on “author” folder. I moved them to “custom” folder but no luck. I check at the plugin settings, folder is readable and everything seems to work “out of the box”. But they aren’t.
I would be grateful, whenever you have the time, if you could give some useful insights of how to fix this.
Thank you,
Eddie.