The forum wants a question first... so I write the question down before I could give a working solution I found 😀
After migrating to Quartus II V17.1 on Windows 10, I noticed that my USB Blaster II was not showing in "Tools / Programmer" window.
I tried to reinstall the driver, unplug the Blaster, restarted Quartus : always same problem. In Device Manager, USB Blaster was displayed as working but Quartus could not see it.
And the solution is finally extremely simple : just start Quartus as Administrator (right-click on the shortcut, then choose "Execute as administrator" even if your Windows account is an admin one..
When you open "Tools/Programmer" menu, you may notice the USB device connection sound (even if the Blaster is already connected). After a few seconds (it takes roughly 5 seconds on my machine, which is quite fast... so be patient 💤 ), the Programmer window opens with the USB Blaster visible and selected by default...
Hope this can help others..