@greeniron - welcome to MobileRead.
That was a problem with very old versions of this plugin but shouldn't be happening nowadays. Either attach your "Generate Cover.json" file from the plugins file or PM/email it to me (you can find my email address inside the zip file at the top of any of the .py files). You find that json file in your calibre configuration folder in the plugins subfolder (Preferences->Misc->Open calibre configuration)
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