MS Word 2016 equation editor: latex mode self-disables
Solution 1:
Type alt+= to enter a math zone and on the math ribbon click on the lower right corner of the Tools section. This brings up the Equation Options dialog. Click on Math Autocorrect and in the Replace text box type \TeX and in the With text box type 24C9 alt+x to enter Ⓣ.
https://blogs.msdn.microsoft.com/murrays/2017/07/30/latex-math-in-office/