This error is returned in case the C/C++ MEX compiler has not been configured in MATLAB after installing a supported compiler. Please refer to the following links for more information:

https://www.mathworks.com/support/requirements/supported-compilers.html
https://www.mathworks.com/help/matlab/matlab_external/changing-default-compiler.html 

This error is also displayed in the following cases:

•  The TRACE32 integration with Simulink cannot find the t32api library in the TRACE32 installation under demo/api/capi/dll (t32api64.dll / t32api.dll for Windows or t32api64.so for Linux)
• The TRACE32 integration with Simulink cannot find the header file t32.h in the TRACE32 installation under demo/api/capi/src