New Cert for company VPN, now openconnect does not work

There is a workaround to use the --servercert option when connecting:

in terminal enter

sudo openconnect --protocol=gp <hostaddress>

and get the message:

Certificate from VPN server "serverhost" failed verification. 
Reason:   signer not found To trust this server in future, perhaps
add this to your command line: --servercert pin-sha256:serverfingerprint 
Enter 'sì' to accept, 'no' to abort; anything else to view: 

and then finally use the fingerprint in your command line option:

openconnect --servercert=sha1:26cfbcdefg... [usual arguments] 

or

openconnect --servercert=sha256:a8cfbcdedeadbeefdeadbeeffg... [usual arguments]

Source https://github.com/dlenski/openconnect/issues/60