You are right. The link you provided in your first communication thread doesn't allow youto download a Composer update. That may be an issue with the Registration Center.
So please try all related links you are seeing under 'My Products' in the Intel Registration Center.
On the left hand row of the product list click on
'Intel Parallel Composer' (https://registrationcenter.intel.com/RegCenter/MySerialNumbers.aspx?id=321)
'Intel Parallel Studio' (https://registrationcenter.intel.com/RegCenter/MySerialNumbers.aspx?id=324)
and try out whether one of themguides you to a validComposer Update 6 download link (file 'composer_update6_setup.exe').
Let me know what you found so that we can investigate the underlying issue with the Composer download.