I haven't used Sonar for a couple of months. During that time, I upgraded the Slate plugs as I normally do with the new updates. Now, when I load any song, Sonar tells me that it cant load the Virtual Mix Rack or Tape Machine. The location of the plugs are exactly the same as they were, and load in three other programs just fine. I tried a complete reinstall of Sonar, deleted and rescanned the vst plug preferences several times, but the plugins still won't load. So, I'm dead in the water on older songs that were close to being complete. 
 
Anyone else run into this problem and know a solution?

Using Windows 10 I the problem of not being able to load the VST 2 version of Slate Mix Rack - But I could load the VST 3 version.  After a Win 10 update was installed I was able to use both VST 2 and VST 3 versions of Mix Rack.
 I don't remember which Windows 10 update that was but it was about 2 months ago.

Thanks for the info. My windows 10 update and Slate plugs are all current. I only have the VST3 plugs in my menus, and loaded into my projects. I'll see if I can load the VST2 just to find out.

I have found the vst3 version of Slate plugs to be troublesome, I use the vst2 flavor.
 

Yeah, try the VST2 version. If it is old enough to be prior to X3, it has to be VST2, but SONAR only tells you the plugin is not there.

has slate been informed?

I'm on the latest version of Sonar Platinum.
 
When VMR was first released, they said that the VST3 was buggy, and urged people to use the VST2 until it was sorted. A while later, Steven confirmed that VST3 was just as stable as VST2. So, I made the switch and never had a problem. The tracks are so huge that I wouldn't be able to run the songs on my comp if I switched to VST2.
 
I'll contact Slate and see if they have a solution.