After launching an application inside a Windows virtual machine, Do Not Disturb mode is activated on the Mac side.
Grayed out Notification Center icon indicates that Do Not Disturb mode has been activated.
To disable Do Not Disturb mode on the Mac do the following:
- Right-click/Control-click on the application icon in the Dock.
- Move the mouse cursor to App Settings menu item and using its submenu uncheck Do Not Disturb.
- As s result, the Notification Center icon should back to normal and Do Not Disturb mode will be deactivated.