Downloading the latest Scala SDKs through the IDE (e.g. 2.12.4 or 2.12.3) just doesn't seem to currently work? (downloading "System" one from http://scala-lang.org/download/ seems to work fine)
Full log: https://bpaste.net/show/78352d7d2a8d
This happens with both W10 and macOS (JDK 8u152) even with a clean install and clean .IntelliJIdea2017.2, .ivy2 and .sbt.