SSL VPN Certificate Error

[FueledByCoffeeDXB]

Activated SSL VPN and followed the steps from the cookbook. However, I am getting an error before I can connect. If I install the cert and chose yes, it will connect and work as normal. But if you turn your PC off and retry, the error will re-appear again!

ERROR: this page requires a secure connection which includes server authentication (Windows)

I have tried creating an acme cert too but it keeps on failing which is annoying, now I can't use the 2 domains we have because it is saying that those were already used.

[rmreddy]

Hi,
Follow the below link how to purchase and import the certificate
https://docs.fortinet.com/document/fortigate/6.2.3/cookbook/825073/purchase-and-import-a-signed-ssl-...

After importing the certificate, you can use that certificate in SSLVPN settings.
While connecting to VPN make sure to connect using domain and make sure the domain is resolving to the IP of fortigate public IP

[fostercarly]

This issue typically happens for a 2-Way TLS, when the certificate sent by the client is expired. In a 2-way TLS, both client and server exchange their public certificates to accomplish the handshake. The client validates the server certificate and the server validates the client certificate. During the TLS handshake if it is found that the client certificate is expired, then the server will send 400 Bad request with the message "The SSL certificate error". The solution for this problem is that procure a new certificate and upload the certificate