Devices not showing in ADE above bookshelves 4.5.12

If your Kobo e-reader is not being recognized by Adobe Digital Editions, try these steps:

Ensure your e-reader's date and time are correct.

De-authorize your computer and e-reader:
• Unplug your Kobo e-reader
• Open Adobe Digital Editions
• De-authorize your computer
• Plug in your Kobo e-reader and de-authorize it   (Mine wasn't "authorized".)

Reconnect and re-authorize:
• Unplug your e-reader
• Plug it back in
• On your e-reader, tap "Connect"
• Open Adobe Digital Editions

• Re-authorize the ADE

• Kobo should appear on your devices list.
.  Under 'Devices', right-click on "Kobo eReader"  (Mine automatically "Authorized" when I clicked on the Kobo device.)
• Click "Authorize Device" and confirm

If the issue persists, try closing and reopening Adobe Digital Editions.

Sources
Fix a Content Locked Error in Adobe Digital Editions – Rakuten Kobo
Add eBooks with Adobe Digital Editions – Rakuten Kobo
-------------------------------------------------------------------------------

If you're still having trouble getting your Kobo e-reader recognized by Adobe Digital Editions, try these additional steps:

Close Adobe Digital Editions completely, then reopen it. Sometimes, your Kobo eReader may not appear under Devices immediately.

If the latest version of Adobe Digital Editions isn't working for your computer, try downloading and using an older version:
• For Mac: Adobe Digital Editions 3.0
• For PC: Adobe Digital Editions 3.0

Re-authorize your eReader. This process can help establish a fresh connection between your device and ADE.

If you encounter any specific error messages, search for them on the official Adobe Digital Editions support page for targeted solutions.

If these steps don't resolve the issue, you may need to contact Kobo Support for further assistance with your specific device.

Source
Add eBooks with Adobe Digital Editions – Rakuten Kobo

I've had the same problem twice now.  The first time I tried different USB ports, but nothing changed.  I restarted my whole laptop, with the Kobo already plugged in.   The Kobo registered on my computer, but once again, not in the "Device" section of ADE.  At least my borrowed books stayed on the Library on the ADE.  Just can't transfer them to Kobo.