Can you try to follow my instruction step by step?
1. Open the uTool.
2. Click on the export tab
3. There’s a folder icon at the top-left side click on this icon, then select your multitrack song location (the mono files what you want to use for the multitrack song)
4. Click on the “add new song” button
5. Now you can add your mono files (left side) to the multitrack song (right side) and you can select which mono file for which cannel.
6. Add some name for your new multitrack file (top-left side)
7. Click on the save and quit button
8. Please check you already attached some USB drive to your PC and you selected that drive on the right side. And please also check, you selected “multitrack songs”
9. Now you can see in the left side your new multitrack song, select this song and simply click on the “export” button
10. Disconnect your USB drive from the PC (if the exporting finished) then connect to the uTrack front panel USB slot and try to play the multitrack song