This posting begs the question: Why do you want SEP 11.0.6005 (RU6a)?
If you are planning to stay with SEP 11 instead of upgrading to SEP 12.1, you will want to be using the latest release which is 11.0.7300 (RU7 MP3).
Once a newer RU (release update) is released, access to older versions is removed from FileConnect. This is by design.
MJD