Change language office 365

+ CategoryInfo : OperationStopped: (:), MicrosoftOnlineException

+ set-msoluser -userprincipalname xxx -preferredlanguage 'en-US'

You will see this error: set-msoluser : Unable to update parameter. If you attempt to do this as an administrator using a Powershell command to set the PreferredLanguage attribute directly like this: set-msoluser -userprincipalname 'xxx' -PreferredLanguage 'en-US'

Users cannot change the display language of the Office 365 portal themselves if they are synced users, and they’ll receive an error.