external 2FA for ftgt ssl vpn

[alsoft]

Hi,

we are sw company, and have own security product (authentication server). It can work like radius + otp (and many others methods) so I try to integrate OTP to ftgt. It works (with free ssl vpn client). But after I try use 2FA online method, with push notification. And here I have problem. Forticlient send AD user name and correct password, mobile app recieve notification, but FortClient instantly shows OTP dialog. With no reason, I not send more validation req. -- UPDATE ---

This is because I have second functional radius server with MS365 MFA on it. And fortigate from unknown reason switch to this, second server, almost instantly after password send. When I change IP of second radius to nonsense, everything works.
Fortios have only 2 parameters I know, timeout in radius definition, and global, remoteauthtimeout. Both set to 120s and not helping.
This seems now like some error in fortigate logic, so I create ticket on it, sorry for this post, I believe in time of writing that this can be free forticlient problem...

Anyone any hint?