Hello,
The packages can be downloaded manually. I have tested this. The downloads appear to start but then fail at some point. After this then cannot synchronize to that repository anymore. There are other repos that complete the synchronization and if I initiate them, they will synchronize properly.
Just to note that this is an automated install using Jenkins and I have used this process many times. There are no problems with the URLs for the repos.
I used the same build process yesterday to build a 3.15 version and the repos sync properly.