Larry, Sorry for the very late post on this.
Before seeing this thread, 2 weeks ago I decide to install SONAR 8 with the works this time using all 4 discs. I got Guitar Rig 3 installed and activated on SONAR, but it was a convoluted process. This is on Windows 10 64-bit.
BTW, when you first launch Guitar Rig, it will show as Guitar Rig 3 Demo, Buy, Activate. When activated, it will become Guitar Rig 3 LE. You cannot active via NI Service Centre now. NI shut that down in 2020. You have to download and install Native Access.
In my SONAR box is the Guitar Rig 3, 25-digit serial number. Also found in the box, is the Guitar Rig 3, 9-digit password for Native Instruments. You must have both. If you have not got the password, you can message Native Instruments for help.
I could not get the latest Native Access to recognise my install of Guitar Rig 3. I had to used Native Access 1.14.1
https://support.native-instruments.com/hc/en-us/articles/360000407909-Native-Access-Legacy-Installers-for-Older-Operating-Systems
Guitar Rig 3.2.1 Win Update fixed activation problems on 64-bit systems I had to download and install Guitar Rig 3.2.1 Win Update to fix it.
https://www.native-instruments.com/en/support/downloads/update-manager/?q=Guitar+Rig+3&t=updates
Type guitar rig 3 in search for products.
Here is the list of legacy products that can still be activated in Native Access. Guitar Rig 3 can be activated.
https://support.native-instruments.com/hc/en-us/articles/360006053397-Service-Center-and-Legacy-Products-End-of-Life
Hope this helps.