Okay... all installed now.
For SilkTone (and anyone else who's interested) here's ther offline activation procedure. It's pretty easy and as I said ealrier I was just following the vid.
1) Go to your store account's Products page using your online computer
2) Click on Connected Products (it's kind of a dropdown above your older products)
3) Click on the Platinum section which will expose all the downloads for Platinum
4) Download whatever you want from the list (if you own previous versions you'll own a lot of that stuff already)
5) If you need the Addictive Drums, Melodyne or other included stuff you have to click the other dropdowns because they are not under the Platinum section but that has nothing to do with registering Sonar.
6) Put all your downloads on an external drive or whatever you use to move files around between systems
7) Right click the Platinum installer and select Run As Administrator (I always use Run As Administrator but a double left click should launch it anyway... you should also close all other programs and turn off your antivirus temporarily)
8) Once you go through all the install windows open Platinum (or Artist or Studio)
9) In the vid it says to create a project but you don't need to do that. Just close the Open dialog if it pops up so you have a blank instance of Sonar
10) In the global menu (at the top of the screen) click Help > Offline Activation > Export Activation Request
11) Choose a location on your computer to save the file generated (like your desktop)
12) Transfer that file to your online computer
13) Log into your Store account again and click Activate
14) Click "Select A File" (if you use script blockers you need to allow the Cakewalk domain for this to work).
15) Browse to wherever you saved the file (like your USB key or desktop)
16) This will generate a new file that you need to download (the vid doesn't really show this)
17) Transfer that file back to your DAW
18) Open Sonar and click Help > Offline Activation > Import Activation Response
19) Browse to wherever you have your new activation file stored and select it
20) Apply it and a Toast message will pop up saying Sonar is now activated. The Offline Activation entry in the Help menu will disappear as well... I'm assuming until your membership lapses.
So a little bit of effort and seems like a lot of steps but it's actually pretty easy.
Cheers.