When I open existing projects in SONAR, or load a project template, I can't hear a guitar plugged into my Scarlett 6i6. The level indicator on the 6i6 lights up, but nothing gets to the computer. If I try to roll the transport, I get the message "Unable to open audio playback device. Device may not support the current project's audio format or may be in use." The project won't play. I should mention here that I have no system sounds, either -- not that I care, but they used to work..
 
The only thing I can think of that's changed recently is the Windows 10 upgrade (did it at the last moment in July) and then the Win 10 Anniversary update. I haven't used the DAW enough to be sure that this is what caused the problem, but I have read here that these updates have been known to reinstall older drivers, change settings, stc., and otherwise wreak havoc with SONAR (for example XLN no longer recognized my machine - fixed that).
 
I do have an old M-Audio card installed, but it is completely disabled in the Windows Sound control panel, as is all the built-in Realtek stuff, and the PC is set to use only the 6i6 for everything. This exact setup has been working without a hiccup for a long time. Can anyone here please point me in the right direction to begin troubleshooting this issue? Many thanks!

Hi Larry,
I had the same problem over the weekend.  I just reinstalled the driver for my audio card ( actually a Roland /Cakewalk VS20), and it worked fine. Good luck! 

Un-install the 6i6 drivers, then re-install. Can't hurt...could help.

Thanks, Tim and Craig.
 
I uninstalled Mix Control 1.8 and the Scarlett driver, then reinstalled both. Now when I open a project template and play the guitar, the signal is getting through from the 6i6 to the computer, showing on all the meters and sounding. But when I try to play an existing project I get the same error as before, to wit "Unable to open audio playback device. Device may not support the current project's audio format or may be in use" and the transport won't roll. There is nothing unusual in the project I'm trying to play, and it worked the last time I tried to listen to it -- a few days ago just before my Windows Anniversary update.
 
So I'm still trying to figure this out. Does anyone have an idea?
 
EDITED TO ADD MORE INFO:
1.) The playback problem appears to apply only to one project. It's an old project that was recorded in SONAR 8.5.3. Just by coincidence I chose it to test my system, and assumed the failure would apply to other projects. I've tried two newer projects, and they play fine. This is good news, but still a problem that must be solved, because I have a bunch of stuff from the old days that I want to be able to use.
2.) On the "bad" project, in Preferences|Audio|Driver Settings, bit depth was set to 24 and greyed out -- I could not change it. Later, after I messed around with sample rate & bit depth in Windows Sound control panel, I discovered that SONAR's bit depth had changed to 16, and was still greyed out.
2.) Also on the "bad" project, in Preferences|Audio|Driver Settings, the "Asio panel..." button does not open Mix Control. It doesn't do anything.
 
Thanks for reading. I'll try any ideas you might have.

I've got nothing. I guess one question would be "do you have any frozen tracks in the old project?"
I'm just wondering if they could be possibly causing a conflict due to a bit depth difference. Outside that, I'd maybe look to see if the old project is expecting a device that's no longer installed on the system. Maybe have a look that the master bus is actually referencing the 6i6. Again, these are all just wild guesses.

Check all ins and outs in that project. If it was made with a different audio interface there could be residual outs that are no longer there. Check Preferences to see that you have the right driver loaded.
 
Once done save the project.  
 

So many people have had audio-related problems after a Windows automatic update that Microsoft posted a how-to-fix-it video:
 

 
When I last had this problem, it only required re-disabling the Realtek onboard interface, which the update had raised from the dead on my behalf. I also had to reset the default sample rate, which the update had switched to 96 KHz

Aside from what Bitflipper mentioned, it could be that some other program (e.g., a browser) already grabbed Windows' audio engine.

Added confusion in red below.
 

Tim Flannagin
I've got nothing. I guess one question would be "do you have any frozen tracks in the old project?"
I'm just wondering if they could be possibly causing a conflict due to a bit depth difference. Outside that, I'd maybe look to see if the old project is expecting a device that's no longer installed on the system. Maybe have a look that the master bus is actually referencing the 6i6. Again, these are all just wild guesses.

Tim - No frozen tracks in the "bad" project. I thought it might be looking for the old M-Audio sound card (see John's suggestion below), but nope.
 

John
Check all ins and outs in that project. If it was made with a different audio interface there could be residual outs that are no longer there. Check Preferences to see that you have the right driver loaded.
 
Once done save the project.  
 

John - As far as I know there is only one driver for the 6i6, and it's loaded in SONAR. All the audio tracks are going to the master bus, which is going to the Scarlett.

bitflipper
So many people have had audio-related problems after a Windows automatic update that Microsoft posted a how-to-fix-it video.
When I last had this problem, it only required re-disabling the Realtek onboard interface, which the update had raised from the dead on my behalf. I also had to reset the default sample rate, which the update had switched to 96 KHz

bitflipper - Ha! I wonder if Microsoft got those videos ready before they pushed out Windows 10. In any case, looking at them has created even more confusion in my mind, because in the "Advanced" Windows properties sheet for the 6i6, I see that I have no 24 bit options, only 16 bit at various sample rates. But the project that doesn't play is set to 16 bit and greyed out, so that's a match and should play; while the (randomly chosen) project that plays just fine is set to 24 bit, which is not a match and therefore shouldn't work. Now I have a headache.

Anderton
Aside from what Bitflipper mentioned, it could be that some other program (e.g., a browser) already grabbed Windows' audio engine.

Craig - So far, every application on this machine (Sound Forge, Chrome, System) has use of the Windows audio engine. Sonar does, too, except for (so far) this one project. I suspect if I dig other oldies out of the archives I will find the same problem. Haven't done that yet, because this whole thing is giving me a headache.

You got off easy, my DAW will not boot after that big anniversary roll up patch! I rolled it back and got it running again. But, I will need to turn off driver authentication so I can install an unsigned driver I think.