Yes. I have the newest version of Sonar Platinum.
This solution didn't work, but to the best of my knowledge this is only happening with this project. I've never encountered it before.
I run:
Sonar Platinum 21.3.00 Build 20 - x64
Windows 8.1
Intel Pentium CPUG 2020T @ 2.50 GHz
4 GB
Steinberg UR12 Interface which probably has absolutely nothing to do with this problem...very strange.
I wonder if I accidently unchecked/checked something on the screen you get when you add a synth?
Ok. As soon as I typed that I went and checked something I should have checked before on this project. I can change synth on other tracks, but not this one. I must have checked something.