Hi
Create a shortcut on you desktop for the program with the missing Icon.
Right click/New/Shortcut etc.
If the new shortcut doesn't have an Icon, right click on the icon and select properties, and then select the Customize tab.
Click on Change Icon and select the Icon you want.
You can navigate to the program file and find the original icon or just pick one.
Once you have the Icon on the desktop right click on it and select Pin to Taskbar.
Remove the old blank icon.
I have this happen every once in a while, I have no idea why the shortcut loses it's connection to the Icon but it happens.
Mike