A possible solution for the issue of the missing characters/operators in MathType's workspace.
The system locale setting, on the Region configurations of Windows, seems to be the key.
In some Windows environments the option 'Beta: Use Unicode UTF-8 for worldwide language support' is enabled, and this might cause you not to see many characters on MathType.
*Note: Save your work and close your programs before trying this procedure. At the end of the steps it will be necessary that you restart your system.
- Open the Windows Control Panel and then choose Region (Region and language/Clock, language and region).
- Go to the Administrative tab and select 'Change system locale...'
- In the next dialog (Region Settings) uncheck the box 'Beta: Use Unicode UTF-8 for worldwide language support' if it is selected, and click OK.
- The next dialog will ask for a restart of your system. If you saved your work and closed your programs, click 'Restart now'.
- Open MathType and try again.
Hopefully this will solve your problem with missing special charaters/operators in MathType.