This is expected behavior and means that the code was generated because it had not been generated before the build. If code was already generated and the model had not changed, it could be reused. There should be no issues with the generated code. You can learn more about Model Reference Rebuild as a performance tool in our documentation: https://www.mathworks.com/help/simulink/gui/rebuild.html
If the message under "Action" is "Failed" instead of "Code Generated" or "Code Generated and Compiled" the code did not generate properly. In this case, more detailed errors should be present in the build log that can be used to troubleshoot the issue.
In 2024b, "Code generation information file does not exist." is replaced with "slprj folder or artifacts were missing." and the "Rebuild Reason" and "Action" swap positions in the build summary table. With this change, the result of the "Action" will be the final text in the summary to avoid confusion that an error occurred.
