Fortigate SSL VPN SAML Authentication Error

Hi Muhammadsaad,

As you mentioned, VPN stuck at 40%. This may occur when FortiClient generates a new pop-up window verifying whether the user wishes to proceed with a non-trusted TLS/SSL certificate.

https://community.fortinet.com/t5/FortiGate/Troubleshooting-Tip-Possible-reasons-for-FortiClient-SSL-VPN/ta-p/211965

Can you please run the below debug commands and try to connect the VPN and share us the output to check further

diagnose debug reset
diagnose debug console timestamp enable
diagnose debug application samld -1
diagnose debug application sslvpn -1
diagnose debug enable

Regards!

well due to some restrictions and secure environment, output can't be shared. Is there any other way

Run the diagnose commands and facing the below error:
Error: 'The identifier of a provider is unknown to #LassoServer'

We have also followed the required steps in order to overcome the error but no luck

If you are ob 7.6.x maybe the issue is another  Agentless VPN (formerly SSL VPN web mode) not supported on FortiGate 40F, 60F, and 90G series models | FortiGate / FortiOS 7.6.3 | Fortinet Document Library

Outside of that with FortiAuthenticator you can have it SAML IdP proxy and if SAML has issues then Oauth OpenID connect could be used.

SAML IdP proxy for Azure | FortiAuthenticator 6.5.0 | Fortinet Document Library

FortiGate SSL VPN Authentication with FortiAuthenticator as IdP Proxy for Azure AD

Creating a remote OAuth server with Azure application ID and authentication key | FortiAuthenticator 6.5.0 | Fortinet Document Library