Newbie help - tracks not playing

I'm a Sonar 7 user recently upgraded to X3. It's a new machine and the VSTs differ on each machine. When I open an old 7 project in X3, some VSTs are reported missing. I use the Replace Synth option, but I get no sound. I've tried just inserting a Synth and assigning the MIDI track to it with the same result. Watching the meters, I know the MIDI tracks are playing, but the meters don't move on the synth track.

I do an Insert Synth to give myself an example and ensure that the ins and outs are similar between it and my non sounding tracks, but I can't get it to sound.

New synths inserted work fine. Old tracks where the VST is present on the new machine work fine.

I can rout the midi to a new synth instance and it works, but I'll have to redo all my automation. I'd rather figure out what I'm doing wrong.