There are times when xliff files need to be updated in both Tridion Docs (TD) and TMS after the translated objects have been retrieved in TD, or there is a problem that causes Translation Organizer an inability to retrieve translated objects from TMS. 

For TD, TMS will need to provide the translated objects to be updated. The updated objects will need to be imported back into TD using the translation option in the Content Importer client tool. 

For all the versions of Content Importer verify what status the object should show after importation (i.e. Translation in Review, Translation Approved) as there is a field that requires this information.