Unable to logon to the server. Your login credentials not be configured properly (-12) SSL

Question

Hello everybody,When trying establish any SSL VPN via "FortiClient SSLVPN", it always answer "Unable to logon to the server. Your login credentials not be configured properly (-12)".It was working fine from several years and suddendly put this error all the time at 80% of the connection. I've tried all answers I've found here, disable cookies control in Internet Explorer, no symbol in the user password and so on, without any success.I've called the support 3 times but I don't have any password to access the customer support space where you can create a ticket number. I've requested reset of this password to send to the login email adress but I never receive the mail reset form ! I've turned several hours in this mess, wondering if it could be any licence issue but support says Fortigate 60C (I'm using), has 10 customer access licence included. When I asked if there was any expiration period, they answer to ask the tech support they can't put me with because I don't have any ticket number ! I am going crazy with this stuff. Is anyone here could simply answer how it can NOT work as it was working fine two days ago without any change in the configuration of the Firewall ??? Thanks you all for your reading and answers.