In case others are experiencing my issue:
IEEE Support Center wrote:
Dear Steven,
Thank you for your patience.
I have checked with our Standards team and they confirmed that there is a newest version of 1584 published November 30 which should be available for you to download but at this moment we are having technical difficulties getting this item posted to Xplore. There is a whole team of us trying to remedy this issue and we will get it updated soon.