Things to check...
Deployment Task
In the Octopus Administration Website, open "Your Project" -> "Process" -> The deployment task.
Check that you have selected to deploy the "IIS Web Site" feature and entered web site name, application pool name (double check that this is correct), the .NET version, and the correct bindings (i.e. port number).
If you are using a specific host name, ensure you have entered that in the binding too (otherwise IIS can't route traffic to the correct site, and the site won't start in IIS).
IIS
Open IIS and see if the website is running. If not, when you attempt to run it you will get a message to explain why. Usually it is because there are multiple sites attempting to run on the same IP/Port combination without a host name to distinguish between them. This is likely to feed back into the deployment task.
Error Logs
If all else fails, check some logs... in particular:
- View the deploymentin Octopus and select "Task Log", then switch on "Verbose" and read through the deployment to see if there is anything amiss
- Check the event logs on the target machine for an error message