Sign-in to FortiGate configuration portal as admin.
Check which Virtual Domain is bound to the network interface.
Open the RADIUS Server configuration for an appropriate Virtual Domain and setup the required settings.
Click Test Connectivity and specify the credentials of Advanced Authentication administrator to test the connection.
Create a user group and bind it to a remote authentication server.
Create user and place in the created group.
Set the Remote Authentication timeout. Default timeout is 5 seconds. Run the following commands in the command line:
config system global
set remoteauthtimeout 45
Set the RADIUS client timeout using the following commands:
config user radius
edit
set timeout 60