SSLVPN authentication problem with LDAP "user logon workstation"

hi

Suppose "user logon workstation" Used in Domain Controller and user names used by LDAP in fortigate. When a username is used in SSLVPN and other Worksation, it encounters message "Error: Permission denied". My question is that 1-fortigate which Name are used to authenticate Domain controller? 2. Is there a way to use simultaneously from LOGON work station and SSLVPN?