In WorldServer, some of the locales/cultures supported in SDL Trados Studio 2017/2019 and WorldServer are not synchronized.
The new set of cultures available in SDL Trados Studio 2017/2019 needs to be integrated in your version of WorldServer. Moreover, you need to map an existing locale to one of the locales.
You can download WorldServer distribution package from SDL FTP site. If you have any problems, please raise a WorldServer support case.
These are the locales supported after installing the SDL Custom Cultures: