SSLVPN - Fortigate -> FortiAuthenticator

Hi there,   I'm configuring a new enviroment of VPNSSL with RADIUS (FortiAuthenticator) users and we want to make the use of user certificates mandatory.   Users and certificates are locally created on FortiAuthenticator and FortiGate request authentication. This scenario is working but the VPN brings up with user certificates configured on FortiClient or Not!   We need to make the use of the certificate mandatory and if the user leaves it blank... doesn't work. Attach some images: