For Google to verify your site, your homepage must be public, and your site cannot be private.

NiCE KM already uses structured data for breadcrumbs as part of Technical SEO automatically handled by NiCE KM. Google added a new Breadcrumbs report to Search Console in September 2019.
The new Breadcrumbs report is showing a Missing field "itemListElement" error for some NiCE KM sites. This error may impact how breadcrumbs appear within Google search rich results.
NiCE KM Engineering is currently investigating to resolve the issue.