Keith,
Where did the install put your AmpliTube3.dll?
Add that location to the "scan" path in "Plug-In Manager" in Sonar,
or move it to "Program Files\Cakewalk\vstplugins"
There is a caveat here.
What is your OS, if x64 are you running Sonar as x32 in x64 OS?
The devil is in the details...
HTH,
T