Hello,
Thanks for the question. Short of modifying the configuration files there is no way to renew the certificate manually. But I will go ahead and submit a feature request for this. If you're having issues with certificates I would recommend reaching out to support as they should be able to guide you on fixing whatever issue you're having.
Kind Regards,
Zach Sylvester
Software Developer
SmarterTools Inc.
www.smartertools.com