Hi,
open your buddypress-nk_NO.po file with a text editor (notepad++ or so) and check you have a plural form for the untranslated string.
The’re several strings containing “members” with a count, but it will be easy to find if you search for “msgid_plural”.
At least, you should find something constructed like this:
#: bp-templates/bp-legacy/buddypress/members/single/groups/invites.php:34
msgctxt "Group member count"
msgid "%d member"
msgid_plural "%d members"
msgstr[0] "%d medlem"
msgstr[1] "%d medlemmer"
Again, note that it is only an example, you may find other strings containing “medlem” that you have eventually to adjust.
The important thing to control is the existence of “%d” and naturally, the presence of the plural form string in the translation.
If you still have trouble after controling/repairing/modifying, it could be possible that it is your theme. To ensure, do the same check in your theme translation.
Other thing to take in account
I’m not 100% sure, but so far i remember, the norvegian buddypress version is not completely translated.
Unfortunately, translate.wordpress.org is actually down and it is impossible to access the plugins translations at this time…
What i expect is that you have an old po file, fully translated, but perhaps not with the most recent changes and updates, which could explain that even if you have plural forms in your translation, they won’t show up in some places.
For ex. because the plural code changed from %s (in your version) to %d or something like that.
To avoid this, you can download the most recent pot file and rename it to buddypress-nk_NO.po.
Then you rename YOUR current version to .pot(with a T), import it to the new file, and adjust or complete the missing strings.
