Word - Equation editor - Mac

MB, thanks for the screen shot. I'm with Wiris, makers of MathType. As you know, and others have correctly pointed out, MathType does not yet work with Catalina. What hasn't been said is that this applies only to editing equations. You should still be able to view equations created in documents under a pre-Catalina OS.

Before proceeding, if Word is open, close it now.

The main font MathType uses for displaying many symbols is the MT Extra font. Since you upgraded your OS from an earlier version to Catalina, you probably already have this font. Still, I'd like you to try reinstalling it. If you have a MathType folder in your Applications folder, go to MathType > Fonts > TrueType. Find the file MT Extra.dfont, and double-click it. (Note: Don't be confused by the similarly-named font Mt Extra Tiger.ttf. Reinstalling that one won't help at all.) After you double-click, it will open in Font Book, and you should see an "Install Font" button in the lower right corner of the pop-up window. Click that to install it. After a few seconds, you'll see it in Font Book under the User fonts. (If you don't have MathType in your Applications folder, I have a copy of MT Extra for Mac on my Dropbox: https://www.dropbox.com/s/anjqrhjhk6jahi8/MT%20Extra.dfont?dl=0. Hopefully that link will show up here.)

Now re-open Word and see if you can at least read the equations.

Note, for creating new equations, there is a MathType add-in, which you'll find if you go to the Insert tab in Word, and under "Get Add-ins" you can search for MathType and add it. Once added, it will appear on Word's Insert tab. This is a different interface than the MathType interface you're used to. It will not edit old MathType equations, but you can create new ones. New equations you create with this add-in will be in the OMML format, which is the same format Word's equation editor uses.