Sorry to hear you are having issues. First check if you Start10 setting is set correctly to use Windowblinds theme.
If that is correctly set. Try rebooting. If it still fail. Please try purge and reinstall Start10, steps as mentioned here: https://forums.stardock.com/486022/start10-support-faq#reinstalling. Just make sure to re-download the latest version from your account. Reboot after the purged. Reinstall, and Reboot again after the installation. Retest it. Report back here.
If needed, do the same for Windowblinds : https://forums.stardock.com/486023/windowblinds-support-faq#reinstalling.
Stardock Community Assistant