Try dragging the file from the right-hand window to the left-hand window. If that doesn't work try downloading the files in question in the cPanel File Manager. If that still doesn't work then it might be part of a few ongoing problems with the boru server, which will be fixed during the major update that has been happening (let us know if this is the case though so that we can see if we can issue a temporary fix for it before doing the upgrades).