Language Files CoursePress Pro & Market Press

Hi,

I've installed Market Press and Course Press Pro and dropped the language files to /wp-content/languages/plugins/ as stated in the tutorial https://premium.wpmudev.org/manuals/using-wpmu-dev/translations/?mksi=b&utm_expid=3606929-94.Ie3dH-CaRwe6MU3VrZsdvw.1 but nothing happens.
Site language is chosen.
Does this only affect new courses and products?

Can you please help?

Thanks and regards,
Barbara