Sorry to hear that you are having trouble.
Things to check:
1. Are you seeing any errors when you hit the URL for the Web UI or does it just hang?
2. Is firewall turned off (iptables, etc) on the host? To turn off iptables, you can run “service iptables stop”.
3. Is Ambari server listening on port 8080? netstat -anp | grep 8080
4. Does this work from the host itself? curl -uadmin:admin http://localhost:8080/api/v1/clusters
5. Do you see any errors in /var/log/ambari-server/ambari-server.log?