Unresponsive MAS For the MAS,…
Number of links with /en/
HTTP/1.1 400 Bad Request
A number of links with /en/ from Mac App Store & App Store give a HTTP/1.1 400 Bad Request
How to find bad links ?
Find links referencing the /en/ using Googledorking :
Conclusion : You can obtain more information about the unresponsive Mas here