SSFE can use wildcard certificates. However, the administrator must ensure that the End User Portal address or FQDN of the SSFE server is only a first-level sub-domain of the wildcard certificate.
If the SSFE domain name as set in the Management Web Console > Administration > System Settings > Domain Name is ssfe.domain.com, a wildcard certificate for *.ssfe.domain.com will work.
On the other hand, a wildcard certificate for *.domain.com will not work because that will mean that the address www.ssfe.domain.com is already a second-level sub-domain of the wildcard certificate. This is because multiple sub-levels of wildcard certificates does not work on most web browsers.