No sound in audio track

Does the project still play normally in X1 or do you no longer have that installed?
 
Are these recorded audio tracks that you don't hear or soft synths? If they're soft synths using Simple Instrument tracks, split them to separate MIDI and synth audio tracks and make sure the synth is loaded and connected in the synth rack and all the routing is correct. And try setting your MIDI Prepare Using Buffer to the old default of 500ms; the new default of 250ms can result in dropped notes or even totally silent synth tracks on some systems. Some users have reported that they need a higher buffer in Platinum than was working well in X1-X3.