Got a reply from Jason at IK Multimedia.
He provided me with a Legacy Authorization manager and instructions how to use it.
All good until it says...
product is already registered on my account and doesn't need authorization.
The problem is...
The Digital ID does NOT match my installation and my registered products in my account.
Therefore...
the authorization code in my account does not unlock SampleTank2 XL.
I probably messed up my installation now.
Next step...
HOW TO COMPLETELY remove any trace of it and start again.
Any help much appreciated...