I've been having problems dragging from the browser at times and I don't know why. But I find if I right click on a track effects bin, Insert FX chain preset and navigate to FX Chain Presets->30th Anniversary CA-X Amps, then I can add them. They're located physically in "D:\CAKEWALK\CONTENT\SONAR Platinum\FX Chain Presets\30th Anniversary CA-X Amps" on my computer.
Also, related to my other posts above, I did get around to installing the vst3 dll and these FX chains now work with the full TH3 version. The FX chains load the vst3 plugin which I verified by the vst header. The sounds are very interesting, useful and pretty cool.