Sonnox G5 licences must be held on a second-generation (iLok2) or third-generation (iLok3) USB device.
If you have upgraded and are still using an original blue/green first-generation iLok1, the plug-ins will not be available to use in your DAW.
iLok2s have been available to purchase for about 5 years now, so it's likely that you have one registered to your iLok account already. If you do need to buy one, please remember to register it to the SAME iLok account as your iLok1, so you can move your licences onto your iLok2 without having to pay a Licence Transfer fee.
iLok3s have been available for a few months, and are fully backwards compatible with iLok2s.