When you switch the language of a document, what really happens is that all the clauses of the document are switched to the language version you have chosen for the document.
If a clause does not have a translation for this particular language, it will be shown in brown/red.
If any concept labels contained therein also lack a translation, they will be receive a pink error notification. For example:
If you notice that your clause does have a translation but it is still being displayed as if it does not, this usually means that the title under which it is grouped does not have a translation. Fixing the content title of a clause is usually the right answer for this.