Cannot change main class or module for IntelliJ run configuration

When creating a run configuration in Intellij, only a few of the modules in my project are offered as options. In addition, I cannot select the Application class I want to use.

When trying to select the Main class, the Ok button is grayed out.

In "Use classpath of module" in the environment configuration, the module I want to use does not appear in the list.

How can I add my module and class to the run configuration?

The module is setup with Maven and Spring.