I can hear the midi fine when I play it, but Guitar Pro used to play the note for me as I tabbed it. It won't do that anymore. How do I fix this?
Look into the settings somewhere you can disable this feature. Find it and enable it.
Peavey 3120
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Look at your volume settings; whenever this happens to me, it's usually that synth is muted or turned down.

Edit: Nevermind, if you hear MIDI fine, then I don't think this is it.
options - preferenced - playback during editing

click on the box if it hasnt been turned on