SUCCESS AT LAST! But be careful. And the problem is Kobo's I think.
This time, before doing a reset or a factory reset, I uninstalled the Kobo Desktop application from my computer. That had been on my computer earlier, from my old Kobo Wifi installation, and when I first set up my new Glo, the setup process caused Kobo website to download and install a copy on top of the old copy (same version as it turns out) of Kobo Desktop on my computer. But the installation wasn't entirely "clean," as I realized this time when the installation and setup process AFTER uninstalling the earlier one, produced some screens I hadn't seen before in the unclean installation ...
So this time, after uninstalling the Kobo software from my computer, I performed a factory rest on the Glo and then went through the re-setup process. It took a bit longer than the first time, but once it finished, FINALLY Adobe Digital Editions recognized the Glo and asked me if I wanted to authorize it (yes!). After authorization, I could then recopy all my DRM epub files from ADE into the Glo, and I have verified that I can now read them all. All seems to be well. Quite a relief after the anger and frustration of the past 24 hours.
Given the grief Kobo Desktop has given me (and the horrible stuff it's done to my iPod app contents and mixing up my iPod bookshelves with my Glo bookshelves without my asking it to), I've decided I'll never use the Kobo Desktop again. From now on, when I buy something from Kobo's ebook website (excellent selection IMO), I'll just download the epub DRM files, load them into ADE, and use ADE to transfer content to the Glo.
I will self-censor the language I want to use concerning Kobo's web and iPod app software ... however I do really like the Glo's features, size, and speed. When it connects with ADE like it's supposed to ...
Thanks again for the suggestion and support. I hope others benefit from my tale of what went wrong and how I fixed it.
BTW for Glo users: the problem started, not out of the box (which was perfect) but when I made the mistake of going into Settings and logging off my Kobo account, figuring I would log back in when I needed to. DON'T GO THERE. Glo immediately said I had to re-setup the device (why, just because I logged out of my web account?? I'll save that screed for my email to Kobo tech support). And that's when all the "fun" began.
Don't log out of your Kobo Account in Glo settings menu, and avoid Kobo Desktop like the plague, once you've finished setting up Glo for the first time. Don't sync with anything using Kobo Desktop; believe me, you'll wish you hadn't (I learned this with my Kobo Wifi and iPod, and it's even worse with Glo and iPod, nightmare city on several levels I won't go into as this isn't a Kobo forum). Do your content installation via ADE. It may be a nightmare when it goes wrong, but until yesterday ADE had been purring like a kitten for me, and is again today. Until someone comes up with something better.
Some software is OK to overwrite, and some software should always be uninstalled before reinstalling or installing a new version. Some software companies (like Kobo) are really sloppy about not clarifying which is the case, for users. Another barbed zinger that Kobo will get from me in a day or so.