Venue 8 Pro Factory Reset

My Venue 8 Pro is a few years old. Upgraded the OS last year to Windows 10.

Yesterday, suddenly the start screen and the all apps screen are both completely empty. I can get to web pages and some settings by using Cortana search, but can't access most apps. I am unable to download, install, and run things as the download seems to work, but I can never get the window that asks me to do the installation.

So, it seems like its time to do a factory reset and return the tablet to its original contents. (I don't store any important info on the tablet - I keep all that on my desktop, so no great loss of data.) But I can't find a way to do a factory reset.

I've tried several things I found on-line. None of these work:
- During boot, go to boot options. I am able to choose Windows Boot Manager, but that just boots the existing Windows 10 system.
- During boot, go to setup. That does not try an auto repair and gives me no useful choices.
- Ran the diagnostics from setup. No problems found.
- From Settings, Recovery tried Reset this PC. Got the message "Could not find the recovery environment. Insert your Windows installation or recovery media."
- From Shift-restart whet to Troubleshoot. But there I did not find an option for Backup and Recovery.

So, How do I reset my Venue 8 Pro to its orignal contents?

Thanks.