My 8.5.3 Producer hasn't worked right for awhile now, which is why I moved to Reaper. But my workflow on Reaper is just not as fast as it was on Sonar. On the plus side, it is very stable. I can do what I want, it just takes longer, and I get tired faster. So, I decided to reinstall Studio 8.5 to see if it might work better for me than Producer. The Plugin Tool had stopped working for me on Pro, which means I couldn'y scan properly. On Studio, it's working, so one problem solved. Also, no crashes so far, another improvement. I imported an orchestral piece of mine done in Pro, and I have all my libraries in and working (GPO, EWSO Gold, Vienna Sp1, Cinematic Strings). Also, it loaded LP64 EQ and MB, and all other Sonar plugs, same as Producer. So, it looks like I have as much functionality in Studio as I had with Producer, and so far no stability issues.
 
If no options to acquire a later version of Sonar than 8.5 are forthcoming, at least I will (hopefully) have a functional 8.5 moving forward. I'm also fooling around with Home Studio 6, see other thread on this). Just passing this on in case it may have relevance for anyone else.

I have had rerun the scan for Vst's because it crashes, especially with Native Instruments Plugins. I suspect that the Native Instument Sevice Center is interrupting the scan. Once I reset and rescan the Plugins get recognized. once that is done I organize in the plugin manager. I get the same issue in both the 32bit and 64bit versions of Sonar Pro 8.5.3.

After that everything seems to work with minimal issues, hopefully it's something as simple as that....if not it sure would be nice to use the Pro version so hopefully you can find a working solution.

The Plug-in Manager and VST scanner are two different programs. They both are in "Shared Utilities." They are used by all Cakewalk DAWs installed on the PC. It used to be possible to get current versions of the utilities by installing the latest demo. This was a good way to get all the fixes to these programs and was recommend by support for users experiencing problems with older versions of SONAR. I am not sure how current the demos are at this time but if they are from last year, it might be worth the trouble to install a demo, any one will do. After installing, save the "Shared Utilities," uninstall the demo and replace the new "Shared Utilities" folder. Unfortunately, early this year (feb?) the Plug-in Manager lost backward compatibility with X-series and older so if the demo is from Feb 2017 or newer, this fix will not work.
 
If you do not want to mess with the demo or it is too new, rename the "Shared Utilities" folder and reinstall SONAR. This should restore the utilities.

Interesting. I'll keep this in mind if Studio does not prove to be adequate. I think I may have more trouble than it might appear. The first Pro install disc won't even work anymore, I have to use a copy I had made awhile back. The other discs are fine. It may be that Studio will be enough for me. It looks like I have all the functionality I need with it. But of course I have barely begun to use it, so time will tell.

So far 8.5 Studio working well, only a problem with Kontakt 5, but I think I can figure that out. However, I have a question: There are two updates to Studio 8.5. Should I install them? One (8.5.2) is 17 mintes. I already downloaded it. The other is 1.7 GB. This looks like it could be the entire program? There are also some others, like Help, Plugin overview, etc.