Turns out I came across a snag. My computer hangs up when downloading apps acquired from the App store, or as part of Windows. I reset, scanned, twiddled and diddled. The only thing I see to do is to un- and reinstall Windows 10 or revert to Windows 8.1. So I've put my stepson on it at the home office in Redmond. Time will tell what comes of it.
Update: A day or two after I posted this, I went to the Microsoft Forums, described by problem, and tried a couple of the scans and stuff suggested there. No joy. Then the next day, last Wednesday, I set up a 'call me' appointment on that site. A technician called, right on time. He was able to take over my PC from his location in the Philippines. He ran the same scans I had run, but knew to start my computer in 'Safe Mode', which the DIY instructions had omitted or I could have fixed it myself. He also removed some malware, and bloatware while he worked on it, all the time with me on the phone.
Long story short (it was a 2 hour process- mostly waiting while the computer ran scans) the problem was resolved. Windows 10 made my Lenovo Yoga 2 into a new computer. I have almost forgotten Windows 8.1 existed.
Apparently enough people had had the 'downloads not downloading' problem that the fix was put in an automatic update that came out over the weekend- or so my step-son told me last night.
I'm a happy camper. Hope all you other Windows users have as good an outcome (preferably without having to call support).
Jim