SharePoint 2013 SP1 retired due to an issue found
It has been found a problem with SP 2013 SP1 that prevent users to install new updates. Please read the official info from the KB
Recomended to not install SP1 until future notification
We have recently uncovered an issue with this Service Pack 1 package that may prevent customers who have Service Pack 1 from deploying future public or cumulative updates. As a precautionary measure, we have deactivated the download page until a new package is published.
Recomended to not install it until future notification
Héctor Calvarro Martín. SharePoint Dev/Core. EMEA Premier Field Engineer.