USB blaster recognized by one Quartus version but not others

Quartus doesn't play well when there are multiple versions installed. The newer versions (since at 14.0 or so) tend to be slightly happier to coexist, however the really old versions (8.0, 9.0) tend to get really finicky about having more than one on the same system.

What is likely happening is that either the system environment variables are pointing to the wrong version, or the JTAG server service is running the old version of the server which will probably be incompatible with the newer version.

In the windows environment variables for the system, what are the values for the following:

QUARTUS_ROOTDIR
QSYS_ROOTDIR
SOPC_KIT_NIOS2

If they are not already, make sure they are all pointing to the 12.0 directory rather than the 8.0 or 9.0 directories.

Additionally, in the windows Services console (type "Services" into the start menu), right click on and open the properties of the "Altera JTAG Server" service. Is the "Path to executable:" pointing to the 12.0 version of Quartus?

If the service is not pointing to the version of Quartus you wish to use, you'll need to reinstall the service. Open command prompt as administrator, and change to the directory shown in the "path to executable:" field. Once there, run the command:

jtagserver --uninstall

Reboot the computer, and then open the command prompt as admin again. This time navigate to the same directory, but for the 12.0 version of the install (e.g. C:\altera\12.0\quartus\bin\). Then run the command:

jtagserver --install

Reboot the computer again.

You should now see in the services that the "Altera JTAG Server" is now registered with a path to the 12.0 version.

Open the quartus programmer and see if your USB blaster is detected. It should hopefully be.