Question Frontend language doesn't agree with Joomla settings

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htaccess: Exists | PHP environment: Max execution time: 30 seconds | Max execution memory: 128M | Max file upload: 8M

Kunena menu details:

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ID	Name	Menutype	Link	Path	In trash
741	Forum	kunenamenu	view=home&defaultmenu=753	forum	No
742	Index	kunenamenu	view=category&layout=list	forum/index	No
743	Recente Onderwerpen	kunenamenu	view=topics&mode=replies	forum/recent	No
744	Ongelezen	kunenamenu	view=topics&layout=unread	forum/unread	No
745	Nieuw Onderwerp	kunenamenu	view=topic&layout=create	forum/newtopic	No
746	Geen Reacties	kunenamenu	view=topics&mode=noreplies	forum/noreplies	No
747	Mijn Onderwerpen	kunenamenu	view=topics&layout=user&mode=default	forum/mylatest	No
748	Profiel	kunenamenu	view=user	forum/profile	No
749	Hulp	kunenamenu	view=misc	forum/help	No
750	Zoeken	kunenamenu	view=search	forum/search	No
751	Forum	mainmenu	Itemid=741	tcn-forum	No
765	Gebruikers	forummenu	view=user&layout=list	beheer/gebruikers	No
766	Statistieken	forummenu	view=statistics	beheer/statistieken	No

Joomla default template details : astroid_template_zero | author: JoomDev | version: 2.0.2 | creationdate: Nov 2018

Kunena default template details : Crypsisb3 | author: Kunena Team | version: 5.1.9 | creationdate: 2019-02-15

Kunena template params:

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DefaultCategoryicon	fa-motorcycle
profileIconset	default
DefaultIconset	tcn_topic_icons
editorIconset	default
borderless	1
tooltips	1
SubjectLengthMessage	80
fullactions	1
quick	1
displayMenu	0
displayDropdownMenu	0
displayDropdownContent	1
displayModule	1
displayBreadcrumb	1
displayAnnouncement	1
displayFooter	1
avatarPosition	left
formRecover	1
labels	0
whoisonlineName	default
avatarType	img-rounded
topicicontype	fa
fontawesome	1
icons	0
socialshare	0
socialsharetag
socialtheme	classic
optional_username	0
writeaccess	0
localstorage	1
IconColor	#383892
IconColorNew	#fd9604
editor	0
video	1
maps	0
emoticons	1
twitter	0
ebay	0
link	1
picture	1
hide	1
spoiler	1
table	1
code	1
quote	1
divider	1
instagram	0
soundcloud	0
confidential	1
hr	1
listitem	1
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subscript	1
numericlist	1
bulletedlist	1
alignright	1
alignleft	1
center	1
underline	1
italic	1
bold	1
strikethrough	1
colors	1
size	1
wysibb	bold,italic,underline,strike,sup,sub,justifyleft,justifycenter,justifyright,|,img,video,link,|,bullist,numlist,|,fontcolor,fontsize,fontfamily,|,quote,code,table,removeFormat
avatarSizeX	40
avatarSizeY	90
avatarSizeXThumb	36
avatarSizeYThumb	36
avatarSizeXWelcome	72
avatarSizeYWelcome	72
avatarSizeXList	36
avatarSizeYList	36
avatarSizeXPost	54
avatarSizeYPost	54
avatarSizeXProfile	100
avatarSizeYProfile	100
templatebyText
templatebyName
templatebyLink

Kunena version detailed: Kunena 5.1.9 | 2019-02-15 [ Kerberos ]
| Kunena detailed configuration:

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Kunena config settings:
board_offline	0
enablerss	1
threads_per_page	20
messages_per_page	20
messages_per_page_search	20
showhistory	1
historylimit	20
shownew	1
disemoticons	0
template	crypsisb3
showannouncement	1
avataroncat	1
catimagepath	category_images
showchildcaticon	0
rtewidth	450
rteheight	300
enableforumjump	1
reportmsg	1
username	0
askemail	0
showemail	0
showuserstats	1
showkarma	0
useredit	1
useredittime	86400
useredittimegrace	600
editmarkup	1
allowsubscriptions	1
subscriptionschecked	1
allowfavorites	1
maxsubject	50
maxsig	300
regonly	0
pubwrite	0
floodprotection	0
mailmod	0
mailadmin	-1
captcha	0
mailfull	0
allowavatarupload	1
allowavatargallery	1
avatarquality	75
avatarsize	2048
imageheight	1024
imagewidth	1024
imagesize	4096
filetypes	txt,rtf,pdf,zip,tar.gz,tgz,tar.bz2,gpx,gdb,itn
filesize	4096
showranking	1
rankimages	1
userlist_rows	30
userlist_online	1
userlist_avatar	1
userlist_posts	1
userlist_karma	0
userlist_email	0
userlist_joindate	1
userlist_lastvisitdate	1
userlist_userhits	0
latestcategory
showstats	1
showwhoisonline	1
showgenstats	1
showpopuserstats	1
popusercount	10
showpopsubjectstats	1
popsubjectcount	10
showspoilertag	1
showvideotag	1
showebaytag	0
trimlongurls	1
trimlongurlsfront	40
trimlongurlsback	20
autoembedyoutube	1
autoembedebay	1
ebaylanguagecode	en-us
sessiontimeout	1800
highlightcode	1
rss_type	recent
rss_timelimit	month
rss_limit	100
rss_included_categories
rss_excluded_categories	bestuur-commissies,leden
rss_specification	rss2.0
rss_allow_html	1
rss_author_format	name
rss_author_in_title	1
rss_word_count	0
rss_old_titles	1
rss_cache	900
defaultpage	recent
default_sort	asc
sef	1
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polltimebtvotes	00:15:00
pollnbvotesbyuser	100
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allow_user_edit_poll	0
maxpersotext	50
ordering_system	replyid
post_dateformat	datetime_today
post_dateformat_hover	datetime
hide_ip	0
imagetypes	jpg,jpeg,gif,png
checkmimetypes	1
imagemimetypes	image/jpeg,image/jpg,image/gif,image/png
imagequality	80
thumbheight	128
thumbwidth	128
hideuserprofileinfo	put_empty
boxghostmessage	0
userdeletetmessage	4
latestcategory_in	1
topicicons	1
debug	0
catsautosubscribed	0
showbannedreason	0
showthankyou	0
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popthankscount	5
mod_see_deleted	1
bbcode_img_secure	image
listcat_show_moderators	0
lightbox	1
show_list_time	0
show_session_type	2
show_session_starttime	1800
userlist_allowed	0
userlist_count_users	1
enable_threaded_layouts	0
category_subscriptions	topic
topic_subscriptions	first
pubprofile	0
thankyou_max	10
email_recipient_count	0
email_recipient_privacy	bcc
captcha_post_limit	1
image_upload	registered
file_upload	registered
topic_layout	flat
time_to_create_page	1
show_imgfiles_manage_profile	0
hold_newusers_posts	0
hold_guest_posts	0
attachment_limit	4
pickup_category	1
article_display	intro
send_emails	1
fallback_english	1
cache	1
cache_time	60
iptracking	1
rss_feedburner_url
autolink	1
access_component	0
statslink_allowed	1
superadmin_userlist	0
legacy_urls	0
attachment_protection	1
categoryicons	1
avatarresizemethod	1
avatarcrop	1
user_report	1
searchtime	365
teaser	0
ebay_language	0
allow_change_subject	0
max_links	6
read_only	0
ratingenabled	0
url_subject_topic	1
log_moderation	1
attach_start	0
attach_end	14
attachment_utf8	1
autoembedsoundcloud	1
emailheader	/media/kunena/email/hero-wide.png
user_status	1
signature	1
personal	1
social	0
plain_email	1
moderator_permdelete	1
avatartypes	gif, jpeg, jpg, png
smartlinking	0
defaultavatar	nophoto.png
defaultavatarsmall	s_nophoto.png
quickreply	1
avataredit	1
activemenuitem
mainmenu_id
home_id
index_id
moderators_id
topiclist_id
misc_id
profile_id
search_id
avatar_type	0
sef_redirect	1
allow_edit_poll	0
use_system_emails	0
autoembedinstagram	1

| Kunena integration settings:

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Kunena - Finder Disabled
Kunena - AltaUserPoints Disabled
Kunena - Community Builder Disabled
Kunena - Easyblog Disabled
Kunena - Easyprofile Disabled
Kunena - Easysocial Disabled
Kunena - Gravatar Disabled
Kunena - JomSocial Disabled
Kunena - Joomla Enabled: access=1 login=1
Kunena - Kunena Enabled: avatar=1 profile=1
Kunena - UddeIM Enabled: private=1

| Joomla! detailed language files installed:

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Joomla! languages installed:
nl-NL	Dutch (nl-NL)
en-GB	English (en-GB)

Third-party components: UddeIM 4.0

Third-party SEF components: None

Plugins: None

Modules: None

[hr]

Our Joomla configuration is set to show content in Dutch (NL-nl) for the frontend. However, in my profile I see quite a lot, but not all, navigation links and buttons displayed in English. I already checked my settings in Kunena and Joomla. Both are set to use Dutch. In our test environment everything was working well regarding language settings.

What am I missing?

Have you installed the newest Kunena language package too?

Neither site has any Kunena language packs installed. So why does it work out of the box on one site and not on the other?

The Kunena installation package contain since many years only the English language. For another languages you must install the language package. Maybe your pages contain still the language from old Kunena versions. The language files will not deleted if you update Kunena but the files are out of date.

Fine. I'll install the required language pack. Yet, the question remains, how come it works on one site but not on the other? Or, let me rephrase, how do I determine what language packs are installed?

From my perspective it looks like both sites (test & production) are identical with respect to Kunena.

et, the question remains, how come it works on one site but not on the other?

I'm sorry, but I can't know it. Maybe you use a Kunena 3rd party template with own language folder, or you've tested Kunena many years ago? In very old Kunena versions was all languages included and it was not needed a extra installation. Check the folder /language/nl-NL whether you find any ini files which beginning with nl-NL.com_kunena.

If you has installed the language package, you see this in the extension manager (as in the image which you've posted).