Don’t ask me why, but there are several places where you need to change the language. The setting in custom.config.php controls the default locale that affects formatting of currency and other data fields.
You also need to change the language in the Settings -> SI Defaults which will change the language for most everything else.
Then there are language settings in the Settings -> Inv Pregs for each invoice type, etc.
When the changes are made, you should have the language changed across the board. If then you see values not translated, it is likely that that info in the lang/nl_NL/lang.php file has not been translated or is missing. If you fix this, it would be helpful if you could send me the updated file to put in the library.
Note that the way the lang files work, is that if wording is in the specified lang file, it is used. If not, the wording in the default lang file (lang/en_US/lang.php) is used.
For example, the $LANG[‘save_inventory_failure’] text exists in the lang/nl_NL/lang.php file but has not been translated. But the $LANG[‘help_company_logo’] text only exists in the lang/en_US/lang.php file, so it is used.
To fix this, you would simple translate the $LANG[‘save_inventory_failure’] text in the lang/nl_NL/lang.php file but need to copy the $LANG[‘help_company_logo’] message to the lang/nl_NL/lang.php file and then translate it. Doing this and providing me with the updated file, I can include it in the library so your changes are lost in future updates and will benefit others that want to use this file.
Note that the info in the lang.php file is alphabetized by the $LANG index value (which must remain as english for the code to work).