WebSite Watcher 20.6 migrated from embedded Internet Explorer to embedded Chromium. Web pages are not displayed with Chromium engine anymore.
More:
https://www.aignes.com/kb/mac_or_linux_version.htm
WebSite-Watcher is a native Windows software, you need Windows to work with WebSite-Watcher.
To use WebSite-Watcher on Mac or Linux computers, you can use a Virtual Machine that runs Windows.
WINE and CrossOver are not supported.
Screenshot (black edges in web preview appeared once I've resized the window):