EezyP
i have VS-100 working fine in Platinum.  Check edit>preferences>control surfaces
Then:
In Port drop-down arrow: click  Control (VS100)
Out Port drop-down arrow: click  Control (VS100)
(not MIDI VS100)
Apply
OK
Mouse click any transport button in the control bar and the transport buttons on the VS100 light and you're away.  I have to do this if my VS100 is not active after I have started Sonar, but if it is already connected viaUSB when Sonar is started, Sonar remembers the settings.  Works for me.  Good luck!

Are you using Windows 10 64-bit and Sonar Platinum?  
I can select under Control Surfaces In Port & Out Port the Control(VS100) but the ACT does not lite.  Mouse clicking the transport PLAY button does not lite the VS100 transport controls.
I can select under Audio Devices Input Drivers VS-100 1-2, 3-4, 5-6, Digital, Main,
and can select Audio Devices Output Drivers VS-100 Out 1-2, 3-4, 5-6. The audio is heard from the headphone jack.
Is there anything else I need to do to make it work?

Obviously I asume you have the latest drivers for VS100 installed - they haven't changed in quite a while I think.
 
What I do (I'm no super-geek-user)...
Power up my VS100.
Power up my PC.
Open Sonar.
Edit>Preferences>MIDI>Devices should show MIDI VS100 and Control VS100 in the inputs and outputs lists.
Under the same MIDI heading in Preferences go down to Control Surfaces.
Under Connected Controller/Surfaces, as a it should show as a controller/surface:VS-100-1, both inport and out port as CONTROLLER(VS100); and, as ACT MIDI CONTROLLER - 1, as both in port and out port MIDI (VS 100 )
 
If VS100 is not shown, click the little yellow star at the top rightof the dialogue box. If your VS100 is USB-ed up, it should be there and you can add it - I occasionally have to do this if my VS100 has been powered down when Sonar was opened.  ACT and transport lights all smiling at me! NB. audio interface can be active even when control surface isn't, which can be confusing at first.
 
That's all I know.  Hope it helps!

EezyP  
Obviously I assume you have the latest drivers for VS100 installed - they haven't changed in quite a while I think 

 
Hi EezyP,
Thank you very much for the procedure to follow.  I did all these steps but the ACT and transport lights NOT all smiling at me! 
 
So I called Cakewalk support and spoke to Joey Adams a very skillful technician who solved the problem.
Background Info on My Setup:  Sonar Platinum (latest version) running on a Surface Pro 3 in Windows 10.
Joey Adams accessed my PC remotely to inspect all the settings in Sonar Platinum and discovered that the
MIDI->Control Surfaces->"Control/Surface drop down list did not have VS-100-1.  Joey brilliantly found the fix on the Roland website to this problem:

V-STUDIO 100, VS-100, SONAR: SYMPTOM: VS-100 DOES NOT APPEAR AS A CONTROL SURFACE SELECTION at  "www.rolandus.com/support/knowledge_base/201975989"

Click the above link, then click the link "VS-100 1.0.1 Control Surface plug-in" to download the file named VS100_1.01_CS.exe.  Run this executable and VS-100-1 will now appear in the Control Surfaces drop down list.
 
Go to Preferences->MIDI->Control Surfaces and click the yellow icon and make these selection:

1.      Controller/Surface = VS-100-1 in drop down list
2.      Input Port = CONTROL(VS-100)
3.      Output Port = CONTROL(VS-100)
4.      Click OK

 
Wow!  The ACT and transport lights all smiling at me!  
 
Additional Information to verify:

1. When you turn on the V-Studio 100 the unit should display the firmware version 1.50.
2. Open Sonar Platinum Preferences->Audio->Driver Settings->ASIO Panel button opens VS-100 Driver Settings.  At the bottom you should see VS-100 Driver Ver.2.0.2.  Click the button Show "README" and this will open your web browser to a page named "VS-100 Driver Ver.2.0.2 for Windows® 10" with additional information. 
   

Thanks,
Steve