Sampler tracks not outputting audio

I have a couple of dozen sampler tracks in a projects. all were working fine.

starting the mixing process, I switched the sampler tracks to group tracks which then output to the stereo out. It was working as advertised.

I then opened the project on a second computer running Cubase 9.5 as well using my dongle, and now,inexplicably, most of the sampler tracks are not outputting audio, meaning no audio shows up on the fader for these channels. The faders I’m referring to are the sampler track faders, not the group track faders, so I know that the issue is with the sampler tracks and not how I set up the group tracks. I also know that

some sampler tracks are outputting audio fine and appear on the group tracks there are supposed to.

has some setting been disabled? what is going?