Why is creating a working IntelliJ project such an ordeal?

I have a project I've just checked out from GitHub.  If I cd into the project directory, I can build it with Maven on the command line; 'mvn install' pulls the dependencies, builds the jar, and installs it in the project target directory.  When then can't IntelliJ even build, let alone run, the project?  Why?  I'm nearing the end of an evaluation of IntelliJ for team-wide use, and the past two days of tearing my hair out have me at the point of "no, we'll just fall back to Eclipse."