Could be:
Incorrect VPN name
User is not allowed to access vpn
Expired Cert
Incorrect fingerprint.
How did you set up the VPN joiner? Did you just export a configuration from the host and add it in? Or did you manually enter the information; if so, did you make some typing errors.
A guide to set up the VPN is available from here:
http://forums.qbik.com/viewtopic.php?p=16108#16108