You are talking about using Microsoft Authenticator to give you the 6-digit 2-factor auth key to login to a VPN using FortiClient, right? If so, no I dont think this is possible. Last time I tried this it let me setup Authenticator with my VPN account but the generated codes were not correct. It is like it uses a similar but slightly-different algorithm that is incompatible with Fortinet's 2FA.
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