If I go to Offline TLS Tool | Elasticsearch Security | Search Guard and click the link to download the offline TLS tool, which is https://releases.floragunn.com/search-guard-tlstool/1.8/search-guard-tlstool-1.8.zip, Firefox tells me:
Web sites prove their identity via certificates. Firefox does not trust this site because it uses a certificate that is not valid for releases.floragunn.com. The certificate is only valid for the following names: *.sgcpanel.com, sgcpanel.com