I understand you are encountering issues while attempting to download the Sourcery G++ Lite third-party software. Regrettably, the website responsible for hosting this third-party content (https://sourcery.mentor.com/) has been inaccessible for several days, affecting the downloadability of various Simulink Support Packages, including this one.
It appears that the site used by the vendor to store these files is currently down, with no clear indication of when or if it will be operational again.
In the meantime, you might find this MATLAB Answer post useful for the latest updates:
