AutoSave switch greyed-out.

this is from:

https://support.office.com/en-us/article/What-is-AutoSave-6d6bd723-ebfd-4e40-b5f6-ae6e8088f7a5?ui=en-US&rs=en-US&ad=US

"AutoSave is enabled when working on a file that is saved to OneDrive, OneDrive for Business, or SharePoint Online. If the file is saved to another location, then AutoSave is disabled. This will happen if your file is on a SharePoint On Premises site, a file server, or saved to a local path like C:.

There are other reasons AutoSave could be disabled as well. For example, if your file is in an older format like .xls, .ppt, or .doc., it will be disabled. It will also be disabled if your presentation is in slide show mode, or if your workbook contains password protection. If AutoSave is disabled, you can always hover over the AutoSave switch and a tooltip will tell you why it's off."

 Well that's not a very helpful approach when USERS for the past 25 years have been allowed to set auto-save and recovery of files to a local disk location to protect their work from unexpected system problems, like the software you own not saving the files where you want them to be saved in the format you want them saved in.

I've been a Microsoft applications user since 1985, yes, 1985.  Only with the new Office 365 versions are we seeing the protection mode of auto-save no longer a user feature but in turn being a Microsoft management feature.  How is this a good idea, what are you thinking?

Yep, that worked. Open it online, Select Open in Powerpoint. A message pops up proudly telling me that Autosaved is now on. 

Pretty typical UX for Microsoft - counter-intuitive and bass ackwards.

This issue still persists; I'm working on a file saved locally on my storage (not primary) HDD. Can't determine why this is off and disabled, other than the program is irritated I'm not electing to use OneDrive? When I saved a copy to my OneDrive folder, magically the option is enabled and turned on, with a little notification telling me that they've got my back.

Sure, document recovery exists but a temporary-storage backup file that another user of my computer could inadvertently discard when they run excel is notthe same as a document that automatically backs-up your active file periodically as you work. This is a public school computer nightmare.

I have the same problem on my desktop, though Autosave on my laptop works fine.  I double checked all the settings to be sure everything was the same on both computers.  The only difference is the desktop has a more recent OneDrive build - 17.3.6998.0830.  The OneDrive build on the laptop is 17.3.6966.08.24. Hmmm.