When compiling nested Maven projects in Idea, sometimes the compiler complains about a missing class file.
This occurs on several occasions, depending which part of a project is compiled and what dependencies have been considered. If the project is large this can easily happen, when a specific class should be compiled without having the complete context available. Besides the tipps such as invalidate caches and the ones I found here and here, editing the build configuration of a project helps. Add the a task “Make Project” and the correct class files should be compiled and available.