Try this:
- Go to "Run > Run Configurations... "
- Select the Webby run configuration
- Change the context field to have two forward slashes instead of just one, i.e., '//'.
I'm not sure Webby was intended to work this way ... but it worked for me. Before making this change I had to use localhost:9091/projectName. After making the change I was able to go to localhost:9091.
Hope it works!