Hi, it looks like that might be an artifact of how you’re starting the app. It might be that the project wasn’t imported into intellij as a Leiningen project. Try reimporting it using File->New->From Existing Sources and make sure you select Leiningen in the menu.
If you start the app in the github repo using lein run from the terminal, you should see something like the following:
2021-04-15 12:29:30.111:INFO::main: Logging initialized @2866ms to org.eclipse.jetty.util.log.StdErrLog
2021-04-15 12:29:30.583:INFO:oejs.Server:main: jetty-9.4.31.v20200723; built: 2020-07-23T17:57:36.812Z; git: 450ba27947e13e66baa8cd1ce7e85a4461cacc1d; jvm 12.0.1+12
2021-04-15 12:29:30.638:INFO:oejs.AbstractConnector:main: Started ServerConnector@2ca132ad{HTTP/1.1, (http/1.1)}{0.0.0.0:3000}
2021-04-15 12:29:30.638:INFO:oejs.Server:main: Started @3393ms
and you’ll be able to navigate to localhost:3000 in the browser. So, the project itself looks like it’s working.