I have the same problem and unfortunately there seems to be no option to manually download the necessary files or change the URL. It seems the only possibility is to either make Mathworks aware of this problem or ask someone at osmocom to restore the URL.
You can also select a web site from the following list
How to Get Best Site Performance
Select the China site (in Chinese or English) for best site performance. Other MathWorks country sites are not optimized for visits from your location.