When opening Safe Exam Browser on a Windows 10 machine, an error labeled as "Invalid Class" will appear.
The issue comes from a corruption within the WMI repository. To fix this, open a command prompt session as administrator and type in the following lines:
Winmgmt /resetrepository
Winmgmt /salvagerepository
Then close command prompt and open Safe Exam Browser. It should now open without any issues.
If any error codes are printed out in command prompt, use this article to decide particular course of action.