After installing MS Office 2016 Pro Plus EN-US, I tried to add some additional languages for proofing. For some languages the "Add" button is grayed. This happened eg for German (Switzerland) and Romanian.

If I try the same by manually downloading the proofing tools for the language and execite it, I get the message saying that it is not compatible with my office version. I tried this for the 32 bit version of Office 2016 and corresponding proofing tools version. (I could not install the 64 version of Office 2016 because I've got Office 2007 installed.)

Any Ideas?