If you're able to SCP to ESX, please SCP the log to ESX first and then retrieve those files from ESX.
If you're able to authenticate (either successful or failed), VI SDK should be working. If you have more than say 20 VMs powering on, it might take time to enumerate all of them, so after clicking "add", please wait for a while and please do not refresh the page or open another session at the same time.
So here's the steps I'd suggest to try again:
1. Restart tomcat
2. Refresh browser
3. Fill up host credentials and click add
4. Wait for it to complete
5. If after a few minutes, it doesn't respond, please provide the log to us.
You may also take a quick look by going to the bottom of /var/www/ioa.log and /var/log/daemon.log and see whether there's any unusual errors/warnings.
Thanks,
Chien-Chia