So this is happening to me now - I tried re-opening Sonar while holding Ctrl+Shift and that didn't seem to help.
I can tell you that there is absolutely nothing wrong with my chain because I open a NEW project fresh, set up a side chain exactly how I have it in the project I'm working on and it works just fine.
Does anyone have any gd clue what the hell is going on here? This has happened to me in the past I literally had to start a new project form scratch and import everything into it. This project is too far along to do that.
Honestly stuff like this has me thinking of going to another DAW. I feel like Sonar has become more and more difficult since Win 10 and such.
I mean in 2017 this shouldn't be an issue.