Fortigate authentication problem


I’ve installed authentication proxy to use 2FA on a Fortigate firewall. When I try to authenticate the user, the first authentication accomplishes successfully and I get a request to provide the Token Code. When I provide it from my , the authentication fails.
I’ve turned on the debug mode and in the authproxy.log file I can see the authentication proxy communicates with the DUO API, but I can’t see any authentication log in the administration console. I 've double-checked the ikey, secret key and API hostname parameters, and they are set correctly.
Did I forgot to do something?