The error 8024001F suggests automatic update fails due to no internet connection. If you don't want to connect to internet, you may disable automatically checking for update in system settings, and then try again.
However, I am not sure whether the failure to install convenience rollup is due to auto-update or not. Maybe the error log is not recorded in Windowsupdate.log, and in this case I don't really know what is causing the problem.
It is also suggested that "April 2015 Servicing Stack Update KB3020369" should be installed as a pre-requisite. Do you have it?