Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
So I ran into this same error while trying to install from an offline CTR setup. I had installed it on this machine the other day, but had to change my install order of a couple different versions of Office for plugin compatibility. When I went to install my O365 Office 2013 CTR, I got this error. Reading through everyone's responses and I kept seeing talk about this proxy shenanigans, it made me realize I've already got all of the files, why do I need to be online? So I disabled my NIC and sure enough, installs just fine.
Don't you just love how there isn't an ISO for this? You know that this went through many layers of approval and they all said the same thing... this command line tool coupled with an XML file is the way to do it.
tl;dr Disable your NIC if you've already got the files downloaded for Click To Run before installing.