Security warning regarding Cisgco AnyConnect Secure Mobility Client

Hi Experts,
While enabling built-in website security and defense of malware threat, I received a security warning in respect of Cisco AnyConnect Secure Mobility Client.

Cisco AnyConnect Secure Mobility Client
Security Warning: Untrusted VPN Server
Certificate!
AnyConnect cannot verify the VPN server: hostname.example.com
Certificate is from an untrusted source.
Connecting to this server may result in a severe security compromise!
Security Risks Explained
Most users do not connect to untrusted VPN servers unless the reason
for the error condition is known.
Always trust this VPN server and import the certificate
Connect Anyway Cancel Connection
Do you have any idea about the Untrusted VPN Server Certificate?
Please guide me to solve the problem.
Thanks in advance.
