I would suggest a couple of diagnosing steps:
1) Please build a simple reproduction model that uses the "MOD" block and see if it indeed includes the "rt_modf.h" header file in the generated code.
2) Once you've done this, please confirm that you can generate an executable using "grt.tlc" with this reproduction model.
3) If the header file is included in the generated code, and the executable build fine, you should look where this header file is located. You should first look into the code generation folder and see if it's there. If it's in the code generation folder, it's possible that the necessary directories are not provided to include for CCS to compile. If it's not in the codegen folder, it could be somewhere else on the MATLAB path and the you might need to use "packNGo" to package all dependencies of the generated code.
For more information on "packNGo" please follow the documentation link below:
If the above steps does not reslove the issue or if you have further questions please submit a Technical support request here: