Dimension Pro

How are you auditioning the sounds? Are you using a midi controller? or are you using the browser to audition midi files with Dim Pro as your synth? In any case, try setting the input to "omni" and then make sure the output on the track is going to the proper buss or master

you have to record something first.

Just as an experiment if you follow these steps do you still get no sound?

1. In the Browser, select the + sign for Insert Synth, select Dimension Pro.
2. Select the simplest configuration of Simple Instrument Track, Synth Property Page and Synth Rack View.
3. Choose a preset in Dimension Pro.
4. For testing purposes either copy and paste you MIDI data you already have into the new Simple Instrument Track or browse to one of the sample MIDI tracks in the browser and drag it to the Simple Instrument Track. Solo the track if you have other tracks.
5. Hit PLAY - it should play that MIDI with the preset sound. 
6. Go back into that instance of Dimensio Pro and select another preset.
7. Repeat step 5

If it does play both presets, then you probably have a routing problem/channel/configuration problem in your existing track it would seem and not a plugin problem.  

This seems like a simple way to rule out at least one possible problem.

HD2774


the track is already recorded and has midi data--I'm just trying to change instruments/sounds

#1. Many instruments on DP are a narrow part of the keyboard so you may be playing on the wrong octave for recorded data.

Check that first.

#2. Can you set echo on and play and DP can be heard?
If so try and record a short piece of that track and play it back.
You can just select and press Q so mute the clip you already have there.

Does that work?

If so, rhen recorded data is possibly on another midi channel or wrong octave on selected instrument.

You can either change octave on DP patch, or better transponse recorded track to correct octave. Set to +12 or -12 on the midi track.