After migrating from IGA 14.5 to V 15.0, the interface used by End-user in Netherlands language is missing.
IGA V 15.0
In IGA v 15.0, removed those languages which we are not supporting
IGA 15.0, they mentioned that supported language list is reduced and the IM installs translated versions of the User Console and online help in the following languages for now
May be considering backward support in 15.0.1, but for now, there is no ETA.
Until then, we can refer to How to Configure Support for Localization document link below.
Also, refer to KB Document link below
https://knowledge.broadcom.com/external/article/9545