MS Word Grammar Checker no longer support Japanese?

I was using MSWord Grammar Checker with Studio 2015 for a while. Then the tool stopped working suddenly in November and I got this message when I ran the verification process.

 
Message
Grammar Checker is not supported ‘Japanese (Japan)’ language
 
Origin
Grammar Checker init
 
I updated Studio to 2017, but this problem persists. I checked the settings on my MSWord 2016, which is in the Japanese subscription version of Office suite called "Office 365 Solo.” Japanese was selected as the language to spell/grammar check. On Studio 2017, MS Grammar Checker was checked in under both Verification areas under Options and Project Settings. Does the error message mean that this tool no longer supports the Japanese language? I hope it's not the case.
 
Noriko Nevins