After installing Windows 10 update KB4346084 or KB4493464, MS Office language detecting doesn’t work anymore. This means that, if you type a text in a different language, Word doesn’t switch to that language, but assumes your text is in the default language (and, consequently, gives a lot of errors). Uninstalling these updates made the feature come back again. I used wushowhide.diagcab to hide the updates, but that is just a temporary workaround. Windows 10 Pro 64-bit; Microsoft Office 365 ProPlus.