BlixYZ
For whatever reason, only absynth shows up as a vst instrument what Im in 64 bit x2.
Sometimes I find that one of my installed plugins is not listed as available in my Sonar Xn Browser.
When this happens, I open the Cakewalk Plugin Manager utility and check to see whether it is listed where expected in the right-hand pane - it usually is.
However, to get it back to being available in the Browser again, I remove the plugin from the list in the right-hand pane in the Plugin Manager and then add it again from the list of installed plugins in the middle pane.
After this, when I am back in Sonar Xn, the "missing" plugin is back in the Browser listing where it should be.
I don't know why this situation arises for me but perhaps this is your case also and this would work for you.