When trying to install from package manager I get the
Could not download package at: http://modx.s3.amazonaws.com/extras/4e56789ef24554514d000021/filedownloadr-1.1.7-pl.transport.zip
When I execute
curl -O http://modx.s3.amazonaws.com/extras/4e56789ef24554514d000021/filedownloadr-1.1.7-pl.transport.zip
in the core/package directory - downloads fine and then I can use the package manager to scan for a local install which it does just fine. Have tries as root and as a normal user to eliminate permissions.
Also have set selinux to permissive to eliminate another possibility.