After a good week of passing the buck back and forth between Sony and Magix, I finally got an email from Magix with a new serial number and authentication code for Noise Reduction 2.0. It is full on and registered under 'My products' on the Magix site.

There you go, then.
Michael

With all the money spent on software programs from Sony you'd think you owned them out right but nope, we are victims of the 'subscription' game. So long as they're in business and if you don't remove/install more than a number of times you'll be fine. But if any of these companies should vanished then we are royally screwed. No serial number will ever be able to authenticate the programs and taken down with them. We're all 'plug-ins' and they are the main program, w/o them we don't work.