So I just built a brand new PC and bought a brand new Impact Nektar - COMPLETELY different interface from my AKAI MPK before....

STILL SAME ISSUE!   I have to reboot now in order to get it to work inside Sonar... yet it works in standalone softsynths.
 
Hmmm.. if it works in standalone softsynths, that eliminates OS and hardware....  what's left... SONAR!   What a joke.

Myself I think it might be the lack of a proper USB midi driver.
One thing I notice is some keyboard controllers come with an actual driver you install and other use some sort of Windows generic driver.. Sound familiar? Right, we would not want this for our audio interfaces.
 
Way up there in this thread I think it was Craig who asked the OP if they had tried using the DIN midi ports. That was never answered and I think was a good idea.  This would rule out USB weirdness. It would also require the controller to use your interfaces midi driver. 
 
I am forever acidentally unplugging my Roland A49 USB cable because it runs across my desk and gets in my way. Same with my Yamaha DX drum kit. The cables are not long enough to put out of my way. 
Way back in this thread the OP posted the notice you get when the cable is un plugged. Sonar seems to keep track of what is hooked up. I've never had either device not work. 
I just plug it back in and Sonar see's it and asks if I want to use it. done. 
 
My Roland keyboard came with a midi usb driver,, so did my Yamaha DX drum kit.
 
But here's the catch-- My Akai Synth Station 25 did not come with a driver and it does not work all the time. I have to re boot Sonar after plugging it in.   So that's my take on USB midi. Don't buy a controller that does not come with a proper driver written for it. It's going to have issues just like a USB mike that uses generic drivers for audio. 

If you are talking about removing the hidden devices here:  http://www.harmonycentral.com/articles/solving-the-windows-midi-port-problem
 
well I did this already on both machines.   

i have a demo version of Reason installed which can see my MIDI controller no problem... so not sure the device manager matters at this point. The problem is CLEARLY Sonar related.  It works in EVERY program besides Sonar until I reboot.
 
Sonar's underbelly still runs on code from the 90's so I'm not surprised.
 

AdamGrossmanLG
So I just built a brand new PC and bought a brand new Impact Nektar - COMPLETELY different interface from my AKAI MPK before....

STILL SAME ISSUE!   I have to reboot now in order to get it to work inside Sonar... yet it works in standalone softsynths.
 
Hmmm.. if it works in standalone softsynths, that eliminates OS and hardware....  what's left... SONAR!   What a joke.

AdamGrossmanLG
Sonar's underbelly still runs on code from the 90's so I'm not surprised.

 
Since this follows you from machine to machine and hardware device to device, there has to be something that is a constant in the formula for the issue to manifest. We can probably get to the bottom of this, but we need to rule possible contributors out logically. Without doing this we couldn't even begin to apply a code side fix.
 
1) You mention that you built your PC. Is there any add-on USB/Peripheral/Bluetooth Adapter devices that you have always used? It could be the most obscure inconsequential part.
2) Besides SONAR, has there been any synth or other software application always installed? Again, it could be the most innocuous utility, we just need to know the entire picture.
3) Are you migrating settings into SONAR or have backed up setup files you go to?
4) Are you  using your own templates?
5) What version(s) of Windows have you been using?
6) Other setup procedures you perform on new systems?
 
Have you tried toggling the settings TStroms mentions above? I read through the entire thread and you don't mention it. I'd recommend that they both be on.
Edit > Preferences > Project > Midi
'Zero Controllers When Play Stops'
'Transmit MIDI Start/Continue/Stop/Clock'


 

Anderton
Well in that case, I'm stumped. Any problems I've encountered in the past were solved by what I mentioned.

As it turns out, it's not all bad. I realized that you were describing a problem that was very similar to an issue I've been having with my Novation SL MkII. I had just assumed that the issue was related to Automap. As it turns out, the article you referenced on Harmony Central fixed my problem. This forum is an absolute gold mine. 

Actually - I get this also - and am looking for control panel - power options... but I dont see any of the advanced menu items shown here in the screenshot..?  

I only have 1 device for my Impact LX49+ so nothing for me to do here, oh and I am able to load up any standalone softsynth and it plays using my keyboard just fine.  Just not Sonar (yet the problem can't be Sonar, Sonar simply is never broken).
 

AdamGrossmanLG
I only have 1 device for my Impact LX49+ so nothing for me to do here, oh and I am able to load up any standalone softsynth and it plays using my keyboard just fine.  Just not Sonar (yet the problem can't be Sonar, Sonar simply is never broken).

I believe your time would be spent more productively trying out Seth's suggestions (and answering his questions), as well as testing with 5-pin DIN plugs, than mischaracterizing what those trying to help you are saying.
 
By your logic, if you're the only one experiencing this particular problem, then the problem must be you.

To answer Seth: 

1) You mention that you built your PC. Is there any add-on USB/Peripheral/Bluetooth Adapter devices that you have alwaysused? It could be the most obscure inconsequential part.  
 
No. Direct USB into the motherboard
 
2) Besides SONAR, has there been any synth or other software application always installed? Again, it could be the most innocuous utility, we just need to know the entire picture.
 
No.  This problem happens the minute opening Sonar.  No softsynths loaded yet and no special MIDI apps running.
 

3) Are you migrating settings into SONAR or have backed up setup files you go to?
 
No.  Fresh install of the OS and Cakewalk software.
 
4) Are you  using your own templates?
 
I do, but this also happens when starting a blank project
 

5) What version(s) of Windows have you been using?
 
Windows 10 Home 64bit

6) Other setup procedures you perform on new systems?
 
Nothing out of the ordinary.  Install Windows, install Sonar, install VSTs, etc...
 
Have you tried toggling the settings TStroms mentions above? I read through the entire thread and you don't mention it. I'd recommend that they both be on.
Edit > Preferences > Project > Midi
'Zero Controllers When Play Stops'
'Transmit MIDI Start/Continue/Stop/Clock'
 
the first setting for 'zero controllers' is not relevant.   I can just load up a MIDI track and no softsynth and it still doesnt  work.  Input is not seen in the activity bar of the track which indicates MIDI data being received.   
"Transmit MIDI Start/Cont/Clock" is disabled - but I didn't change that... it has always been disabled.
 
I will tell you what works though.  Simply going to Device Manager and "uninstalling" the MIDI controller and then doing a "Scan for new hardware changes" then restarting Sonar.   However, like I said earlier - all my other standalone synths are able to see my MIDI keyboard just fine when this problem happens, just not Sonar.  

Is Sonar using some sort of MIDI port caching instead of detecting which port to use each time?  Seems to be something like this.   
How can it be that EVERY OTHER PIECE OF SOFTWARE can be played using my MIDI controller and just SONAR cant until I do this Device Manager trick (or reboot)?