ConfigMgr 1606 – Unable to modify language configuration
When running Configuration Manager current branch 1606 you might run into a situation where you cannot modify the language configuration of a site. The option is simply greyed out, preventing you from adding any client or server languages.
The reason to why this is happening can be found in the ConfigMgrSetupWizard.log (hat tip to fellow MVP Roger Zander for pointing this out). Here we see an entry indicating that setup detected that client piloting is enabled for the site and as a result the modify language configuration option will be disabled.
So if we want to make any language modifications we need to promote the pre-production client to production first. This can be done in the administration workspace in the updates and servicing node.
Once the previous step is completed we can run the Setup Wizard again and in Site Maintenance the modify language configuration option is no longer greyed out. Adding client and server languages is possible.
Conclusion: you cannot change the language settings as long as the pre-production package has not been promoted.
The underlying reason for this is that we cannot apply language pack MSP files for the newer client to an older client version. When in piloting mode the new binaries have been updated everywhere, except for the client folder for production. Adding new client language packs would copy the newer language pack MSP files from cd.latest to the client folder that still has an older client version. These language pack files are not compatible with that older client – and as a result would be deleted.
Hope it helps!