How do I re establish Opus back to my purchased copy after transferring all my data and programs to a new computer, now I have an evaluation version
You have to re-install your certificate which you should have received by email when you purchased Opus. See Help -> License Manager.
All I have is the Registration Code and have used the License Mngr but it requires a Product Token which unfortunately has floated into the ether during the changeover.
You don't need a product token. Those are only used when getting licences from boxed versions or third-party resellers (and similar). Once used, they give you a licence code and certificate like you would get if you buy the program direct from the GPSoftware website. Whichever way you go, you end up with a registration code and certificate file in the end.
The certificate file is what the licence manager needs.
If you've lost it, you can get it again here: https://www.gpsoft.com.au/DScripts/lostcode.asp