Autosave had stopped on my PC and after searching high and low for an answer it occurred to me where the problem might be. Microsoft had tried several times to install update 1709 on my computer which kept failing. I got tired of the constant reminders to reboot my computer for an update that didn't work so I went into the Services.msc and disabled Windows Update. Everything was fine for a while but then Autosave stopped working. Apparently Windows Update was causing Autosave to fail because when I enabled Windows Update, Autosave started working again. Like a giant chess game!