Hello Margrethe,
Thanks for going Pro and welcome to the forums! Let me try to help you with this issue.
Events is also defined in another file, namely wp-content\plugins\the-events-calendar\lang\the-events-calendar-nb_NO.po
Try changing it there as well and let me know the outcome.
Also, if you would like your translations to stick after a plugin update, then I recommend placing these 4 files to the wp-content\languages\plugins\ folder.
the-events-calendar-nb_NO.po
the-events-calendar-nb_NO.mo
tribe-events-calendar-pro-nb_NO.po
tribe-events-calendar-pro-nb_NO.mo
You can find more details about this in this article:
How Do I Update the Calendar’s Language Translations?
Please, let me know if you need any more help.
Cheers,
Andras