Cubase 4.5 'no valid licence' issue on a Mac.

I’m trying to get my home studio up and running again on a Mac Pro desktop (OS10.6.8) and have installed Cubase 4.5. I have the USB dongle plugged in, eLicenser shows a valid licence (confirmed on steinberg.net), but when I try to run the prog I get a ‘no valid license’ error message (see attached Screenshot). I’ve read through all sorts of articles and FAQs and have got nowhere. I’m asking for help here as Steinberg support have yet to respond 10 days after submitting a ticket. There’s probably something obvious I’m missing - can anyone help? Thanks.
Screen shot 2017-03-24 at 18.49.09.jpg