We all know Microsoft Management Console (MMC) manages snap-ins in Windows OS. Snap-ins such as Group Policy Editor, Device Manager, Event Viewer etc. etc. comes under MMC management. Thus if a snap-in is not working, you may need to troubleshoot MMC rather than the snap-in.
Recently, we came around an issue where an error occurs in a snap-in and MMC has to unfortunately unload it to prevent your machine from any unexpected harm. In some cases, this might also be related as snap-in failed to initialize.
The exact error message is as follows, in this case:
MMC has detected an error in snap-in and will unload it.
As you can see in the above shown error message, you’ve two options. You can either report the error and shut down MMC or unload the snap-in and let MMC be running. Most of these kind of errors can be solve by simply rebooting your system. You may run built-in troubleshooters in Windows 10, such as Hardware and Devices, System Maintenance troubleshooters to deal this issue.
However, if the problem still occurs even after restarting/troubleshooting the machine, you can try the fixes mentioned below:
FIX: ‘MMC Has Detected An Error In A Snap-in And Will Unload It’ In Windows 10/8/7
FIX It Using System Properties
1. Press + R and type sysdm.cpl in Run. Click OK or press Enter key.
2. In System Properties window, switch to Advanced tab, click Environment Variables.
3. Next, in the Environment Variables sheet, under System variables, highlight Path Variable, then click Edit.
4. Finally, add the following values to the Variable value and click OK. Make sure you do not remove or change existing Variable value here.
Once done, reboot the machine and the issue should be fixed then.
Hope this helps!