You may find when you enable vistor mode on the Check Point object that the port is not listening when you run the command

netstat -anp | grep vpnd | grep [your port]

This can be down to one of the following :

1. The devices management GUI is also listening on that port. For SPLAT use the command 'webui [port] enable' to change the port.
2. You have not installed the correct license
3. You have not pushed the policy after enabling vistor mode.
4. You have not added the gateway into the remote access community.