Since it came up as non-activate it probably got marked as bad in the Sonar plug-in dateabase.
Some iLok plug-ins have this issue if they are not enabled before Cakewalk's plug-in Scan.
Now that you've activated your new plug-in..,
Least technical fix:
Go into Sonar Preferences, under File under VST Settings and click reset.
Then rescan your plug-ins.
More technical:
Go into registry,
locate plugin under HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR\Cakewalk VST X64\Inventory (change as appropriate if using 32 bit version of Sonar or earlier version of Sonar)
Check to see if "isBad" is set to "1" - if so change to "0", then rescan
(Edit)
Note: you can avoid issues like this if you authorize your plug-ins before they get scanned with Cakewalk's VST plug-in scanner.
Use Seib's Savhost (
http://www.hermannseib.com/english/savihost.htm) or IL's MiniHost to run & authorize the plug-in before firing up Sonar.